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*
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* accompanied this code).
*
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*
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package java.util;
import java.io.Serializable;
import java.io.IOException;
import java.lang.reflect.Array;
/**
* This class consists exclusively of static methods that operate on or return
* collections. It contains polymorphic algorithms that operate on
* collections, "wrappers", which return a new collection backed by a
* specified collection, and a few other odds and ends.
*
* The methods of this class all throw a NullPointerException
* if the collections or class objects provided to them are null.
*
*
The documentation for the polymorphic algorithms contained in this class
* generally includes a brief description of the implementation. Such
* descriptions should be regarded as implementation notes, rather than
* parts of the specification. Implementors should feel free to
* substitute other algorithms, so long as the specification itself is adhered
* to. (For example, the algorithm used by sort does not have to be
* a mergesort, but it does have to be stable.)
*
*
The "destructive" algorithms contained in this class, that is, the
* algorithms that modify the collection on which they operate, are specified
* to throw UnsupportedOperationException if the collection does not
* support the appropriate mutation primitive(s), such as the set
* method. These algorithms may, but are not required to, throw this
* exception if an invocation would have no effect on the collection. For
* example, invoking the sort method on an unmodifiable list that is
* already sorted may or may not throw UnsupportedOperationException.
*
*
This class is a member of the
*
* Java Collections Framework.
*
* @author Josh Bloch
* @author Neal Gafter
* @see Collection
* @see Set
* @see List
* @see Map
* @since 1.2
*/
public class Collections {
// Suppresses default constructor, ensuring non-instantiability.
private Collections() {
}
// Algorithms
/*
* Tuning parameters for algorithms - Many of the List algorithms have
* two implementations, one of which is appropriate for RandomAccess
* lists, the other for "sequential." Often, the random access variant
* yields better performance on small sequential access lists. The
* tuning parameters below determine the cutoff point for what constitutes
* a "small" sequential access list for each algorithm. The values below
* were empirically determined to work well for LinkedList. Hopefully
* they should be reasonable for other sequential access List
* implementations. Those doing performance work on this code would
* do well to validate the values of these parameters from time to time.
* (The first word of each tuning parameter name is the algorithm to which
* it applies.)
*/
private static final int BINARYSEARCH_THRESHOLD = 5000;
private static final int REVERSE_THRESHOLD = 18;
private static final int SHUFFLE_THRESHOLD = 5;
private static final int FILL_THRESHOLD = 25;
private static final int ROTATE_THRESHOLD = 100;
private static final int COPY_THRESHOLD = 10;
private static final int REPLACEALL_THRESHOLD = 11;
private static final int INDEXOFSUBLIST_THRESHOLD = 35;
/**
* Sorts the specified list into ascending order, according to the
* {@linkplain Comparable natural ordering} of its elements.
* All elements in the list must implement the {@link Comparable}
* interface. Furthermore, all elements in the list must be
* mutually comparable (that is, {@code e1.compareTo(e2)}
* must not throw a {@code ClassCastException} for any elements
* {@code e1} and {@code e2} in the list).
*
*
This sort is guaranteed to be stable: equal elements will
* not be reordered as a result of the sort.
*
*
The specified list must be modifiable, but need not be resizable.
*
*
Implementation note: This implementation is a stable, adaptive,
* iterative mergesort that requires far fewer than n lg(n) comparisons
* when the input array is partially sorted, while offering the
* performance of a traditional mergesort when the input array is
* randomly ordered. If the input array is nearly sorted, the
* implementation requires approximately n comparisons. Temporary
* storage requirements vary from a small constant for nearly sorted
* input arrays to n/2 object references for randomly ordered input
* arrays.
*
*
The implementation takes equal advantage of ascending and
* descending order in its input array, and can take advantage of
* ascending and descending order in different parts of the same
* input array. It is well-suited to merging two or more sorted arrays:
* simply concatenate the arrays and sort the resulting array.
*
*
The implementation was adapted from Tim Peters's list sort for Python
* (
* TimSort). It uses techiques from Peter McIlroy's "Optimistic
* Sorting and Information Theoretic Complexity", in Proceedings of the
* Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
* January 1993.
*
*
This implementation dumps the specified list into an array, sorts
* the array, and iterates over the list resetting each element
* from the corresponding position in the array. This avoids the
* n2 log(n) performance that would result from attempting
* to sort a linked list in place.
*
* @param list the list to be sorted.
* @throws ClassCastException if the list contains elements that are not
* mutually comparable (for example, strings and integers).
* @throws UnsupportedOperationException if the specified list's
* list-iterator does not support the {@code set} operation.
* @throws IllegalArgumentException (optional) if the implementation
* detects that the natural ordering of the list elements is
* found to violate the {@link Comparable} contract
*/
public static > void sort(List list) {
Object[] a = list.toArray();
Arrays.sort(a);
ListIterator i = list.listIterator();
for (int j=0; jmutually
* comparable using the specified comparator (that is,
* {@code c.compare(e1, e2)} must not throw a {@code ClassCastException}
* for any elements {@code e1} and {@code e2} in the list).
*
* This sort is guaranteed to be stable: equal elements will
* not be reordered as a result of the sort.
*
*
The specified list must be modifiable, but need not be resizable.
*
*
Implementation note: This implementation is a stable, adaptive,
* iterative mergesort that requires far fewer than n lg(n) comparisons
* when the input array is partially sorted, while offering the
* performance of a traditional mergesort when the input array is
* randomly ordered. If the input array is nearly sorted, the
* implementation requires approximately n comparisons. Temporary
* storage requirements vary from a small constant for nearly sorted
* input arrays to n/2 object references for randomly ordered input
* arrays.
*
*
The implementation takes equal advantage of ascending and
* descending order in its input array, and can take advantage of
* ascending and descending order in different parts of the same
* input array. It is well-suited to merging two or more sorted arrays:
* simply concatenate the arrays and sort the resulting array.
*
*
The implementation was adapted from Tim Peters's list sort for Python
* (
* TimSort). It uses techiques from Peter McIlroy's "Optimistic
* Sorting and Information Theoretic Complexity", in Proceedings of the
* Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
* January 1993.
*
*
This implementation dumps the specified list into an array, sorts
* the array, and iterates over the list resetting each element
* from the corresponding position in the array. This avoids the
* n2 log(n) performance that would result from attempting
* to sort a linked list in place.
*
* @param list the list to be sorted.
* @param c the comparator to determine the order of the list. A
* {@code null} value indicates that the elements' natural
* ordering should be used.
* @throws ClassCastException if the list contains elements that are not
* mutually comparable using the specified comparator.
* @throws UnsupportedOperationException if the specified list's
* list-iterator does not support the {@code set} operation.
* @throws IllegalArgumentException (optional) if the comparator is
* found to violate the {@link Comparator} contract
*/
public static void sort(List list, Comparator c) {
Object[] a = list.toArray();
Arrays.sort(a, (Comparator)c);
ListIterator i = list.listIterator();
for (int j=0; jThis method runs in log(n) time for a "random access" list (which
* provides near-constant-time positional access). If the specified list
* does not implement the {@link RandomAccess} interface and is large,
* this method will do an iterator-based binary search that performs
* O(n) link traversals and O(log n) element comparisons.
*
* @param list the list to be searched.
* @param key the key to be searched for.
* @return the index of the search key, if it is contained in the list;
* otherwise, (-(insertion point) - 1). The
* insertion point is defined as the point at which the
* key would be inserted into the list: the index of the first
* element greater than the key, or list.size() if all
* elements in the list are less than the specified key. Note
* that this guarantees that the return value will be >= 0 if
* and only if the key is found.
* @throws ClassCastException if the list contains elements that are not
* mutually comparable (for example, strings and
* integers), or the search key is not mutually comparable
* with the elements of the list.
*/
public static
int binarySearch(List> list, T key) {
if (list instanceof RandomAccess || list.size()
int indexedBinarySearch(List> list, T key)
{
int low = 0;
int high = list.size()-1;
while (low <= high) {
int mid = (low + high) >>> 1;
Comparable midVal = list.get(mid);
int cmp = midVal.compareTo(key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
private static
int iteratorBinarySearch(List> list, T key)
{
int low = 0;
int high = list.size()-1;
ListIterator> i = list.listIterator();
while (low <= high) {
int mid = (low + high) >>> 1;
Comparable midVal = get(i, mid);
int cmp = midVal.compareTo(key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
/**
* Gets the ith element from the given list by repositioning the specified
* list listIterator.
*/
private static T get(ListIterator i, int index) {
T obj = null;
int pos = i.nextIndex();
if (pos <= index) {
do {
obj = i.next();
} while (pos++ < index);
} else {
do {
obj = i.previous();
} while (--pos > index);
}
return obj;
}
/**
* Searches the specified list for the specified object using the binary
* search algorithm. The list must be sorted into ascending order
* according to the specified comparator (as by the
* {@link #sort(List, Comparator) sort(List, Comparator)}
* method), prior to making this call. If it is
* not sorted, the results are undefined. If the list contains multiple
* elements equal to the specified object, there is no guarantee which one
* will be found.
*
* This method runs in log(n) time for a "random access" list (which
* provides near-constant-time positional access). If the specified list
* does not implement the {@link RandomAccess} interface and is large,
* this method will do an iterator-based binary search that performs
* O(n) link traversals and O(log n) element comparisons.
*
* @param list the list to be searched.
* @param key the key to be searched for.
* @param c the comparator by which the list is ordered.
* A null value indicates that the elements'
* {@linkplain Comparable natural ordering} should be used.
* @return the index of the search key, if it is contained in the list;
* otherwise, (-(insertion point) - 1). The
* insertion point is defined as the point at which the
* key would be inserted into the list: the index of the first
* element greater than the key, or list.size() if all
* elements in the list are less than the specified key. Note
* that this guarantees that the return value will be >= 0 if
* and only if the key is found.
* @throws ClassCastException if the list contains elements that are not
* mutually comparable using the specified comparator,
* or the search key is not mutually comparable with the
* elements of the list using this comparator.
*/
public static int binarySearch(List list, T key, Comparator c) {
if (c==null)
return binarySearch((List) list, key);
if (list instanceof RandomAccess || list.size() int indexedBinarySearch(List l, T key, Comparator c) {
int low = 0;
int high = l.size()-1;
while (low <= high) {
int mid = (low + high) >>> 1;
T midVal = l.get(mid);
int cmp = c.compare(midVal, key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
private static int iteratorBinarySearch(List l, T key, Comparator c) {
int low = 0;
int high = l.size()-1;
ListIterator i = l.listIterator();
while (low <= high) {
int mid = (low + high) >>> 1;
T midVal = get(i, mid);
int cmp = c.compare(midVal, key);
if (cmp < 0)
low = mid + 1;
else if (cmp > 0)
high = mid - 1;
else
return mid; // key found
}
return -(low + 1); // key not found
}
private interface SelfComparable extends Comparable {}
/**
* Reverses the order of the elements in the specified list.
*
* This method runs in linear time.
*
* @param list the list whose elements are to be reversed.
* @throws UnsupportedOperationException if the specified list or
* its list-iterator does not support the set operation.
*/
public static void reverse(List list) {
int size = list.size();
if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) {
for (int i=0, mid=size>>1, j=size-1; i>1; i
*
* The hedge "approximately" is used in the foregoing description because
* default source of randomness is only approximately an unbiased source
* of independently chosen bits. If it were a perfect source of randomly
* chosen bits, then the algorithm would choose permutations with perfect
* uniformity.
*
* This implementation traverses the list backwards, from the last element
* up to the second, repeatedly swapping a randomly selected element into
* the "current position". Elements are randomly selected from the
* portion of the list that runs from the first element to the current
* position, inclusive.
*
* This method runs in linear time. If the specified list does not
* implement the {@link RandomAccess} interface and is large, this
* implementation dumps the specified list into an array before shuffling
* it, and dumps the shuffled array back into the list. This avoids the
* quadratic behavior that would result from shuffling a "sequential
* access" list in place.
*
* @param list the list to be shuffled.
* @throws UnsupportedOperationException if the specified list or
* its list-iterator does not support the set operation.
*/
public static void shuffle(List list) {
Random rnd = r;
if (rnd == null)
r = rnd = new Random();
shuffle(list, rnd);
}
private static Random r;
/**
* Randomly permute the specified list using the specified source of
* randomness. All permutations occur with equal likelihood
* assuming that the source of randomness is fair.
*
* This implementation traverses the list backwards, from the last element
* up to the second, repeatedly swapping a randomly selected element into
* the "current position". Elements are randomly selected from the
* portion of the list that runs from the first element to the current
* position, inclusive.
*
* This method runs in linear time. If the specified list does not
* implement the {@link RandomAccess} interface and is large, this
* implementation dumps the specified list into an array before shuffling
* it, and dumps the shuffled array back into the list. This avoids the
* quadratic behavior that would result from shuffling a "sequential
* access" list in place.
*
* @param list the list to be shuffled.
* @param rnd the source of randomness to use to shuffle the list.
* @throws UnsupportedOperationException if the specified list or its
* list-iterator does not support the set operation.
*/
public static void shuffle(List list, Random rnd) {
int size = list.size();
if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) {
for (int i=size; i>1; i--)
swap(list, i-1, rnd.nextInt(i));
} else {
Object arr[] = list.toArray();
// Shuffle array
for (int i=size; i>1; i--)
swap(arr, i-1, rnd.nextInt(i));
// Dump array back into list
ListIterator it = list.listIterator();
for (int i=0; ii or j
* is out of range (i < 0 || i >= list.size()
* || j < 0 || j >= list.size()).
* @since 1.4
*/
public static void swap(List list, int i, int j) {
final List l = list;
l.set(i, l.set(j, l.get(i)));
}
/**
* Swaps the two specified elements in the specified array.
*/
private static void swap(Object[] arr, int i, int j) {
Object tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
/**
* Replaces all of the elements of the specified list with the specified
* element.
*
* This method runs in linear time.
*
* @param list the list to be filled with the specified element.
* @param obj The element with which to fill the specified list.
* @throws UnsupportedOperationException if the specified list or its
* list-iterator does not support the set operation.
*/
public static void fill(List list, T obj) {
int size = list.size();
if (size < FILL_THRESHOLD || list instanceof RandomAccess) {
for (int i=0; i itr = list.listIterator();
for (int i=0; i
*
* This method runs in linear time.
*
* @param dest The destination list.
* @param src The source list.
* @throws IndexOutOfBoundsException if the destination list is too small
* to contain the entire source List.
* @throws UnsupportedOperationException if the destination list's
* list-iterator does not support the set operation.
*/
public static void copy(List dest, List src) {
int srcSize = src.size();
if (srcSize > dest.size())
throw new IndexOutOfBoundsException("Source does not fit in dest");
if (srcSize < COPY_THRESHOLD ||
(src instanceof RandomAccess && dest instanceof RandomAccess)) {
for (int i=0; i di=dest.listIterator();
ListIterator si=src.listIterator();
for (int i=0; inatural ordering of its elements. All elements in the
* collection must implement the Comparable interface.
* Furthermore, all elements in the collection must be mutually
* comparable (that is, e1.compareTo(e2) must not throw a
* ClassCastException for any elements e1 and
* e2 in the collection).
*
* This method iterates over the entire collection, hence it requires
* time proportional to the size of the collection.
*
* @param coll the collection whose minimum element is to be determined.
* @return the minimum element of the given collection, according
* to the natural ordering of its elements.
* @throws ClassCastException if the collection contains elements that are
* not mutually comparable (for example, strings and
* integers).
* @throws NoSuchElementException if the collection is empty.
* @see Comparable
*/
public static > T min(Collection coll) {
Iterator i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (next.compareTo(candidate) < 0)
candidate = next;
}
return candidate;
}
/**
* Returns the minimum element of the given collection, according to the
* order induced by the specified comparator. All elements in the
* collection must be mutually comparable by the specified
* comparator (that is, comp.compare(e1, e2) must not throw a
* ClassCastException for any elements e1 and
* e2 in the collection).
*
* This method iterates over the entire collection, hence it requires
* time proportional to the size of the collection.
*
* @param coll the collection whose minimum element is to be determined.
* @param comp the comparator with which to determine the minimum element.
* A null value indicates that the elements' natural
* ordering should be used.
* @return the minimum element of the given collection, according
* to the specified comparator.
* @throws ClassCastException if the collection contains elements that are
* not mutually comparable using the specified comparator.
* @throws NoSuchElementException if the collection is empty.
* @see Comparable
*/
public static T min(Collection coll, Comparator comp) {
if (comp==null)
return (T)min((Collection) (Collection) coll);
Iterator i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (comp.compare(next, candidate) < 0)
candidate = next;
}
return candidate;
}
/**
* Returns the maximum element of the given collection, according to the
* natural ordering of its elements. All elements in the
* collection must implement the Comparable interface.
* Furthermore, all elements in the collection must be mutually
* comparable (that is, e1.compareTo(e2) must not throw a
* ClassCastException for any elements e1 and
* e2 in the collection).
*
* This method iterates over the entire collection, hence it requires
* time proportional to the size of the collection.
*
* @param coll the collection whose maximum element is to be determined.
* @return the maximum element of the given collection, according
* to the natural ordering of its elements.
* @throws ClassCastException if the collection contains elements that are
* not mutually comparable (for example, strings and
* integers).
* @throws NoSuchElementException if the collection is empty.
* @see Comparable
*/
public static > T max(Collection coll) {
Iterator i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (next.compareTo(candidate) > 0)
candidate = next;
}
return candidate;
}
/**
* Returns the maximum element of the given collection, according to the
* order induced by the specified comparator. All elements in the
* collection must be mutually comparable by the specified
* comparator (that is, comp.compare(e1, e2) must not throw a
* ClassCastException for any elements e1 and
* e2 in the collection).
*
* This method iterates over the entire collection, hence it requires
* time proportional to the size of the collection.
*
* @param coll the collection whose maximum element is to be determined.
* @param comp the comparator with which to determine the maximum element.
* A null value indicates that the elements' natural
* ordering should be used.
* @return the maximum element of the given collection, according
* to the specified comparator.
* @throws ClassCastException if the collection contains elements that are
* not mutually comparable using the specified comparator.
* @throws NoSuchElementException if the collection is empty.
* @see Comparable
*/
public static T max(Collection coll, Comparator comp) {
if (comp==null)
return (T)max((Collection) (Collection) coll);
Iterator i = coll.iterator();
T candidate = i.next();
while (i.hasNext()) {
T next = i.next();
if (comp.compare(next, candidate) > 0)
candidate = next;
}
return candidate;
}
/**
* Rotates the elements in the specified list by the specified distance.
* After calling this method, the element at index i will be
* the element previously at index (i - distance) mod
* list.size(), for all values of i between 0
* and list.size()-1, inclusive. (This method has no effect on
* the size of the list.)
*
* For example, suppose list comprises [t, a, n, k, s].
* After invoking Collections.rotate(list, 1) (or
* Collections.rotate(list, -4)), list will comprise
* [s, t, a, n, k].
*
*
Note that this method can usefully be applied to sublists to
* move one or more elements within a list while preserving the
* order of the remaining elements. For example, the following idiom
* moves the element at index j forward to position
* k (which must be greater than or equal to j):
*
* Collections.rotate(list.subList(j, k+1), -1);
*
* To make this concrete, suppose list comprises
* [a, b, c, d, e]. To move the element at index 1
* (b) forward two positions, perform the following invocation:
*
* Collections.rotate(l.subList(1, 4), -1);
*
* The resulting list is [a, c, d, b, e].
*
* To move more than one element forward, increase the absolute value
* of the rotation distance. To move elements backward, use a positive
* shift distance.
*
*
If the specified list is small or implements the {@link
* RandomAccess} interface, this implementation exchanges the first
* element into the location it should go, and then repeatedly exchanges
* the displaced element into the location it should go until a displaced
* element is swapped into the first element. If necessary, the process
* is repeated on the second and successive elements, until the rotation
* is complete. If the specified list is large and doesn't implement the
* RandomAccess interface, this implementation breaks the
* list into two sublist views around index -distance mod size.
* Then the {@link #reverse(List)} method is invoked on each sublist view,
* and finally it is invoked on the entire list. For a more complete
* description of both algorithms, see Section 2.3 of Jon Bentley's
* Programming Pearls (Addison-Wesley, 1986).
*
* @param list the list to be rotated.
* @param distance the distance to rotate the list. There are no
* constraints on this value; it may be zero, negative, or
* greater than list.size().
* @throws UnsupportedOperationException if the specified list or
* its list-iterator does not support the set operation.
* @since 1.4
*/
public static void rotate(List list, int distance) {
if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD)
rotate1(list, distance);
else
rotate2(list, distance);
}
private static void rotate1(List list, int distance) {
int size = list.size();
if (size == 0)
return;
distance = distance % size;
if (distance < 0)
distance += size;
if (distance == 0)
return;
for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
T displaced = list.get(cycleStart);
int i = cycleStart;
do {
i += distance;
if (i >= size)
i -= size;
displaced = list.set(i, displaced);
nMoved ++;
} while (i != cycleStart);
}
}
private static void rotate2(List list, int distance) {
int size = list.size();
if (size == 0)
return;
int mid = -distance % size;
if (mid < 0)
mid += size;
if (mid == 0)
return;
reverse(list.subList(0, mid));
reverse(list.subList(mid, size));
reverse(list);
}
/**
* Replaces all occurrences of one specified value in a list with another.
* More formally, replaces with newVal each element e
* in list such that
* (oldVal==null ? e==null : oldVal.equals(e)).
* (This method has no effect on the size of the list.)
*
* @param list the list in which replacement is to occur.
* @param oldVal the old value to be replaced.
* @param newVal the new value with which oldVal is to be
* replaced.
* @return true if list contained one or more elements
* e such that
* (oldVal==null ? e==null : oldVal.equals(e)).
* @throws UnsupportedOperationException if the specified list or
* its list-iterator does not support the set operation.
* @since 1.4
*/
public static boolean replaceAll(List list, T oldVal, T newVal) {
boolean result = false;
int size = list.size();
if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) {
if (oldVal==null) {
for (int i=0; i itr=list.listIterator();
if (oldVal==null) {
for (int i=0; ii
* such that source.subList(i, i+target.size()).equals(target),
* or -1 if there is no such index. (Returns -1 if
* target.size() > source.size().)
*
* This implementation uses the "brute force" technique of scanning
* over the source list, looking for a match with the target at each
* location in turn.
*
* @param source the list in which to search for the first occurrence
* of target.
* @param target the list to search for as a subList of source.
* @return the starting position of the first occurrence of the specified
* target list within the specified source list, or -1 if there
* is no such occurrence.
* @since 1.4
*/
public static int indexOfSubList(List source, List target) {
int sourceSize = source.size();
int targetSize = target.size();
int maxCandidate = sourceSize - targetSize;
if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
(source instanceof RandomAccess&&target instanceof RandomAccess)) {
nextCand:
for (int candidate = 0; candidate <= maxCandidate; candidate++) {
for (int i=0, j=candidate; i si = source.listIterator();
nextCand:
for (int candidate = 0; candidate <= maxCandidate; candidate++) {
ListIterator ti = target.listIterator();
for (int i=0; ii
* such that source.subList(i, i+target.size()).equals(target),
* or -1 if there is no such index. (Returns -1 if
* target.size() > source.size().)
*
* This implementation uses the "brute force" technique of iterating
* over the source list, looking for a match with the target at each
* location in turn.
*
* @param source the list in which to search for the last occurrence
* of target.
* @param target the list to search for as a subList of source.
* @return the starting position of the last occurrence of the specified
* target list within the specified source list, or -1 if there
* is no such occurrence.
* @since 1.4
*/
public static int lastIndexOfSubList(List source, List target) {
int sourceSize = source.size();
int targetSize = target.size();
int maxCandidate = sourceSize - targetSize;
if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
source instanceof RandomAccess) { // Index access version
nextCand:
for (int candidate = maxCandidate; candidate >= 0; candidate--) {
for (int i=0, j=candidate; i si = source.listIterator(maxCandidate);
nextCand:
for (int candidate = maxCandidate; candidate >= 0; candidate--) {
ListIterator ti = target.listIterator();
for (int i=0; iUnsupportedOperationException.
*
* The returned collection does not pass the hashCode and equals
* operations through to the backing collection, but relies on
* Object's equals and hashCode methods. This
* is necessary to preserve the contracts of these operations in the case
* that the backing collection is a set or a list.
*
* The returned collection will be serializable if the specified collection
* is serializable.
*
* @param c the collection for which an unmodifiable view is to be
* returned.
* @return an unmodifiable view of the specified collection.
*/
public static Collection unmodifiableCollection(Collection c) {
return new UnmodifiableCollection<>(c);
}
/**
* @serial include
*/
static class UnmodifiableCollection implements Collection, Serializable {
private static final long serialVersionUID = 1820017752578914078L;
final Collection c;
UnmodifiableCollection(Collection c) {
if (c==null)
throw new NullPointerException();
this.c = c;
}
public int size() {return c.size();}
public boolean isEmpty() {return c.isEmpty();}
public boolean contains(Object o) {return c.contains(o);}
public Object[] toArray() {return c.toArray();}
public T[] toArray(T[] a) {return c.toArray(a);}
public String toString() {return c.toString();}
public Iterator iterator() {
return new Iterator() {
private final Iterator i = c.iterator();
public boolean hasNext() {return i.hasNext();}
public E next() {return i.next();}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
public boolean add(E e) {
throw new UnsupportedOperationException();
}
public boolean remove(Object o) {
throw new UnsupportedOperationException();
}
public boolean containsAll(Collection coll) {
return c.containsAll(coll);
}
public boolean addAll(Collection coll) {
throw new UnsupportedOperationException();
}
public boolean removeAll(Collection coll) {
throw new UnsupportedOperationException();
}
public boolean retainAll(Collection coll) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
}
/**
* Returns an unmodifiable view of the specified set. This method allows
* modules to provide users with "read-only" access to internal sets.
* Query operations on the returned set "read through" to the specified
* set, and attempts to modify the returned set, whether direct or via its
* iterator, result in an UnsupportedOperationException.
*
* The returned set will be serializable if the specified set
* is serializable.
*
* @param s the set for which an unmodifiable view is to be returned.
* @return an unmodifiable view of the specified set.
*/
public static Set unmodifiableSet(Set s) {
return new UnmodifiableSet<>(s);
}
/**
* @serial include
*/
static class UnmodifiableSet extends UnmodifiableCollection
implements Set, Serializable {
private static final long serialVersionUID = -9215047833775013803L;
UnmodifiableSet(Set s) {super(s);}
public boolean equals(Object o) {return o == this || c.equals(o);}
public int hashCode() {return c.hashCode();}
}
/**
* Returns an unmodifiable view of the specified sorted set. This method
* allows modules to provide users with "read-only" access to internal
* sorted sets. Query operations on the returned sorted set "read
* through" to the specified sorted set. Attempts to modify the returned
* sorted set, whether direct, via its iterator, or via its
* subSet, headSet, or tailSet views, result in
* an UnsupportedOperationException.
*
* The returned sorted set will be serializable if the specified sorted set
* is serializable.
*
* @param s the sorted set for which an unmodifiable view is to be
* returned.
* @return an unmodifiable view of the specified sorted set.
*/
public static SortedSet unmodifiableSortedSet(SortedSet s) {
return new UnmodifiableSortedSet<>(s);
}
/**
* @serial include
*/
static class UnmodifiableSortedSet
extends UnmodifiableSet
implements SortedSet, Serializable {
private static final long serialVersionUID = -4929149591599911165L;
private final SortedSet ss;
UnmodifiableSortedSet(SortedSet s) {super(s); ss = s;}
public Comparator comparator() {return ss.comparator();}
public SortedSet subSet(E fromElement, E toElement) {
return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
}
public SortedSet headSet(E toElement) {
return new UnmodifiableSortedSet<>(ss.headSet(toElement));
}
public SortedSet tailSet(E fromElement) {
return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
}
public E first() {return ss.first();}
public E last() {return ss.last();}
}
/**
* Returns an unmodifiable view of the specified list. This method allows
* modules to provide users with "read-only" access to internal
* lists. Query operations on the returned list "read through" to the
* specified list, and attempts to modify the returned list, whether
* direct or via its iterator, result in an
* UnsupportedOperationException.
*
* The returned list will be serializable if the specified list
* is serializable. Similarly, the returned list will implement
* {@link RandomAccess} if the specified list does.
*
* @param list the list for which an unmodifiable view is to be returned.
* @return an unmodifiable view of the specified list.
*/
public static List unmodifiableList(List list) {
return (list instanceof RandomAccess ?
new UnmodifiableRandomAccessList<>(list) :
new UnmodifiableList<>(list));
}
/**
* @serial include
*/
static class UnmodifiableList extends UnmodifiableCollection
implements List {
private static final long serialVersionUID = -283967356065247728L;
final List list;
UnmodifiableList(List list) {
super(list);
this.list = list;
}
public boolean equals(Object o) {return o == this || list.equals(o);}
public int hashCode() {return list.hashCode();}
public E get(int index) {return list.get(index);}
public E set(int index, E element) {
throw new UnsupportedOperationException();
}
public void add(int index, E element) {
throw new UnsupportedOperationException();
}
public E remove(int index) {
throw new UnsupportedOperationException();
}
public int indexOf(Object o) {return list.indexOf(o);}
public int lastIndexOf(Object o) {return list.lastIndexOf(o);}
public boolean addAll(int index, Collection c) {
throw new UnsupportedOperationException();
}
public ListIterator listIterator() {return listIterator(0);}
public ListIterator listIterator(final int index) {
return new ListIterator() {
private final ListIterator i
= list.listIterator(index);
public boolean hasNext() {return i.hasNext();}
public E next() {return i.next();}
public boolean hasPrevious() {return i.hasPrevious();}
public E previous() {return i.previous();}
public int nextIndex() {return i.nextIndex();}
public int previousIndex() {return i.previousIndex();}
public void remove() {
throw new UnsupportedOperationException();
}
public void set(E e) {
throw new UnsupportedOperationException();
}
public void add(E e) {
throw new UnsupportedOperationException();
}
};
}
public List subList(int fromIndex, int toIndex) {
return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
}
/**
* UnmodifiableRandomAccessList instances are serialized as
* UnmodifiableList instances to allow them to be deserialized
* in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
* This method inverts the transformation. As a beneficial
* side-effect, it also grafts the RandomAccess marker onto
* UnmodifiableList instances that were serialized in pre-1.4 JREs.
*
* Note: Unfortunately, UnmodifiableRandomAccessList instances
* serialized in 1.4.1 and deserialized in 1.4 will become
* UnmodifiableList instances, as this method was missing in 1.4.
*/
private Object readResolve() {
return (list instanceof RandomAccess
? new UnmodifiableRandomAccessList<>(list)
: this);
}
}
/**
* @serial include
*/
static class UnmodifiableRandomAccessList extends UnmodifiableList
implements RandomAccess
{
UnmodifiableRandomAccessList(List list) {
super(list);
}
public List subList(int fromIndex, int toIndex) {
return new UnmodifiableRandomAccessList<>(
list.subList(fromIndex, toIndex));
}
private static final long serialVersionUID = -2542308836966382001L;
/**
* Allows instances to be deserialized in pre-1.4 JREs (which do
* not have UnmodifiableRandomAccessList). UnmodifiableList has
* a readResolve method that inverts this transformation upon
* deserialization.
*/
private Object writeReplace() {
return new UnmodifiableList<>(list);
}
}
/**
* Returns an unmodifiable view of the specified map. This method
* allows modules to provide users with "read-only" access to internal
* maps. Query operations on the returned map "read through"
* to the specified map, and attempts to modify the returned
* map, whether direct or via its collection views, result in an
* UnsupportedOperationException.
*
* The returned map will be serializable if the specified map
* is serializable.
*
* @param m the map for which an unmodifiable view is to be returned.
* @return an unmodifiable view of the specified map.
*/
public static Map unmodifiableMap(Map m) {
return new UnmodifiableMap<>(m);
}
/**
* @serial include
*/
private static class UnmodifiableMap implements Map, Serializable {
private static final long serialVersionUID = -1034234728574286014L;
private final Map m;
UnmodifiableMap(Map m) {
if (m==null)
throw new NullPointerException();
this.m = m;
}
public int size() {return m.size();}
public boolean isEmpty() {return m.isEmpty();}
public boolean containsKey(Object key) {return m.containsKey(key);}
public boolean containsValue(Object val) {return m.containsValue(val);}
public V get(Object key) {return m.get(key);}
public V put(K key, V value) {
throw new UnsupportedOperationException();
}
public V remove(Object key) {
throw new UnsupportedOperationException();
}
public void putAll(Map m) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
private transient Set keySet = null;
private transient Set> entrySet = null;
private transient Collection values = null;
public Set keySet() {
if (keySet==null)
keySet = unmodifiableSet(m.keySet());
return keySet;
}
public Set> entrySet() {
if (entrySet==null)
entrySet = new UnmodifiableEntrySet<>(m.entrySet());
return entrySet;
}
public Collection values() {
if (values==null)
values = unmodifiableCollection(m.values());
return values;
}
public boolean equals(Object o) {return o == this || m.equals(o);}
public int hashCode() {return m.hashCode();}
public String toString() {return m.toString();}
/**
* We need this class in addition to UnmodifiableSet as
* Map.Entries themselves permit modification of the backing Map
* via their setValue operation. This class is subtle: there are
* many possible attacks that must be thwarted.
*
* @serial include
*/
static class UnmodifiableEntrySet
extends UnmodifiableSet> {
private static final long serialVersionUID = 7854390611657943733L;
UnmodifiableEntrySet(Set> s) {
super((Set)s);
}
public Iterator> iterator() {
return new Iterator>() {
private final Iterator> i = c.iterator();
public boolean hasNext() {
return i.hasNext();
}
public Map.Entry next() {
return new UnmodifiableEntry<>(i.next());
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
public Object[] toArray() {
Object[] a = c.toArray();
for (int i=0; i((Map.Entry)a[i]);
return a;
}
public T[] toArray(T[] a) {
// We don't pass a to c.toArray, to avoid window of
// vulnerability wherein an unscrupulous multithreaded client
// could get his hands on raw (unwrapped) Entries from c.
Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
for (int i=0; i((Map.Entry)arr[i]);
if (arr.length > a.length)
return (T[])arr;
System.arraycopy(arr, 0, a, 0, arr.length);
if (a.length > arr.length)
a[arr.length] = null;
return a;
}
/**
* This method is overridden to protect the backing set against
* an object with a nefarious equals function that senses
* that the equality-candidate is Map.Entry and calls its
* setValue method.
*/
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
return c.contains(
new UnmodifiableEntry<>((Map.Entry) o));
}
/**
* The next two methods are overridden to protect against
* an unscrupulous List whose contains(Object o) method senses
* when o is a Map.Entry, and calls o.setValue.
*/
public boolean containsAll(Collection coll) {
for (Object e : coll) {
if (!contains(e)) // Invokes safe contains() above
return false;
}
return true;
}
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Set))
return false;
Set s = (Set) o;
if (s.size() != c.size())
return false;
return containsAll(s); // Invokes safe containsAll() above
}
/**
* This "wrapper class" serves two purposes: it prevents
* the client from modifying the backing Map, by short-circuiting
* the setValue method, and it protects the backing Map against
* an ill-behaved Map.Entry that attempts to modify another
* Map Entry when asked to perform an equality check.
*/
private static class UnmodifiableEntry implements Map.Entry {
private Map.Entry e;
UnmodifiableEntry(Map.Entry e) {this.e = e;}
public K getKey() {return e.getKey();}
public V getValue() {return e.getValue();}
public V setValue(V value) {
throw new UnsupportedOperationException();
}
public int hashCode() {return e.hashCode();}
public boolean equals(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry t = (Map.Entry)o;
return eq(e.getKey(), t.getKey()) &&
eq(e.getValue(), t.getValue());
}
public String toString() {return e.toString();}
}
}
}
/**
* Returns an unmodifiable view of the specified sorted map. This method
* allows modules to provide users with "read-only" access to internal
* sorted maps. Query operations on the returned sorted map "read through"
* to the specified sorted map. Attempts to modify the returned
* sorted map, whether direct, via its collection views, or via its
* subMap, headMap, or tailMap views, result in
* an UnsupportedOperationException.
*
* The returned sorted map will be serializable if the specified sorted map
* is serializable.
*
* @param m the sorted map for which an unmodifiable view is to be
* returned.
* @return an unmodifiable view of the specified sorted map.
*/
public static SortedMap unmodifiableSortedMap(SortedMap m) {
return new UnmodifiableSortedMap<>(m);
}
/**
* @serial include
*/
static class UnmodifiableSortedMap
extends UnmodifiableMap
implements SortedMap, Serializable {
private static final long serialVersionUID = -8806743815996713206L;
private final SortedMap sm;
UnmodifiableSortedMap(SortedMap m) {super(m); sm = m;}
public Comparator comparator() {return sm.comparator();}
public SortedMap subMap(K fromKey, K toKey) {
return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey));
}
public SortedMap headMap(K toKey) {
return new UnmodifiableSortedMap<>(sm.headMap(toKey));
}
public SortedMap tailMap(K fromKey) {
return new UnmodifiableSortedMap<>(sm.tailMap(fromKey));
}
public K firstKey() {return sm.firstKey();}
public K lastKey() {return sm.lastKey();}
}
// Synch Wrappers
/**
* Returns a synchronized (thread-safe) collection backed by the specified
* collection. In order to guarantee serial access, it is critical that
* all access to the backing collection is accomplished
* through the returned collection.
*
* It is imperative that the user manually synchronize on the returned
* collection when iterating over it:
*
* Collection c = Collections.synchronizedCollection(myCollection);
* ...
* synchronized (c) {
* Iterator i = c.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*
* Failure to follow this advice may result in non-deterministic behavior.
*
* The returned collection does not pass the hashCode
* and equals operations through to the backing collection, but
* relies on Object's equals and hashCode methods. This is
* necessary to preserve the contracts of these operations in the case
* that the backing collection is a set or a list.
*
* The returned collection will be serializable if the specified collection
* is serializable.
*
* @param c the collection to be "wrapped" in a synchronized collection.
* @return a synchronized view of the specified collection.
*/
public static Collection synchronizedCollection(Collection c) {
return new SynchronizedCollection<>(c);
}
static Collection synchronizedCollection(Collection c, Object mutex) {
return new SynchronizedCollection<>(c, mutex);
}
/**
* @serial include
*/
static class SynchronizedCollection implements Collection, Serializable {
private static final long serialVersionUID = 3053995032091335093L;
final Collection c; // Backing Collection
final Object mutex; // Object on which to synchronize
SynchronizedCollection(Collection c) {
if (c==null)
throw new NullPointerException();
this.c = c;
mutex = this;
}
SynchronizedCollection(Collection c, Object mutex) {
this.c = c;
this.mutex = mutex;
}
public int size() {
synchronized (mutex) {return c.size();}
}
public boolean isEmpty() {
synchronized (mutex) {return c.isEmpty();}
}
public boolean contains(Object o) {
synchronized (mutex) {return c.contains(o);}
}
public Object[] toArray() {
synchronized (mutex) {return c.toArray();}
}
public T[] toArray(T[] a) {
synchronized (mutex) {return c.toArray(a);}
}
public Iterator iterator() {
return c.iterator(); // Must be manually synched by user!
}
public boolean add(E e) {
synchronized (mutex) {return c.add(e);}
}
public boolean remove(Object o) {
synchronized (mutex) {return c.remove(o);}
}
public boolean containsAll(Collection coll) {
synchronized (mutex) {return c.containsAll(coll);}
}
public boolean addAll(Collection coll) {
synchronized (mutex) {return c.addAll(coll);}
}
public boolean removeAll(Collection coll) {
synchronized (mutex) {return c.removeAll(coll);}
}
public boolean retainAll(Collection coll) {
synchronized (mutex) {return c.retainAll(coll);}
}
public void clear() {
synchronized (mutex) {c.clear();}
}
public String toString() {
synchronized (mutex) {return c.toString();}
}
}
/**
* Returns a synchronized (thread-safe) set backed by the specified
* set. In order to guarantee serial access, it is critical that
* all access to the backing set is accomplished
* through the returned set.
*
* It is imperative that the user manually synchronize on the returned
* set when iterating over it:
*
* Set s = Collections.synchronizedSet(new HashSet());
* ...
* synchronized (s) {
* Iterator i = s.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*
* Failure to follow this advice may result in non-deterministic behavior.
*
* The returned set will be serializable if the specified set is
* serializable.
*
* @param s the set to be "wrapped" in a synchronized set.
* @return a synchronized view of the specified set.
*/
public static Set synchronizedSet(Set s) {
return new SynchronizedSet<>(s);
}
static Set synchronizedSet(Set s, Object mutex) {
return new SynchronizedSet<>(s, mutex);
}
/**
* @serial include
*/
static class SynchronizedSet
extends SynchronizedCollection
implements Set {
private static final long serialVersionUID = 487447009682186044L;
SynchronizedSet(Set s) {
super(s);
}
SynchronizedSet(Set s, Object mutex) {
super(s, mutex);
}
public boolean equals(Object o) {
synchronized (mutex) {return c.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return c.hashCode();}
}
}
/**
* Returns a synchronized (thread-safe) sorted set backed by the specified
* sorted set. In order to guarantee serial access, it is critical that
* all access to the backing sorted set is accomplished
* through the returned sorted set (or its views).
*
* It is imperative that the user manually synchronize on the returned
* sorted set when iterating over it or any of its subSet,
* headSet, or tailSet views.
*
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
* ...
* synchronized (s) {
* Iterator i = s.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*
* or:
*
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
* SortedSet s2 = s.headSet(foo);
* ...
* synchronized (s) { // Note: s, not s2!!!
* Iterator i = s2.iterator(); // Must be in the synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*
* Failure to follow this advice may result in non-deterministic behavior.
*
* The returned sorted set will be serializable if the specified
* sorted set is serializable.
*
* @param s the sorted set to be "wrapped" in a synchronized sorted set.
* @return a synchronized view of the specified sorted set.
*/
public static SortedSet synchronizedSortedSet(SortedSet s) {
return new SynchronizedSortedSet<>(s);
}
/**
* @serial include
*/
static class SynchronizedSortedSet
extends SynchronizedSet
implements SortedSet
{
private static final long serialVersionUID = 8695801310862127406L;
private final SortedSet ss;
SynchronizedSortedSet(SortedSet s) {
super(s);
ss = s;
}
SynchronizedSortedSet(SortedSet s, Object mutex) {
super(s, mutex);
ss = s;
}
public Comparator comparator() {
synchronized (mutex) {return ss.comparator();}
}
public SortedSet subSet(E fromElement, E toElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(
ss.subSet(fromElement, toElement), mutex);
}
}
public SortedSet headSet(E toElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
}
}
public SortedSet tailSet(E fromElement) {
synchronized (mutex) {
return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex);
}
}
public E first() {
synchronized (mutex) {return ss.first();}
}
public E last() {
synchronized (mutex) {return ss.last();}
}
}
/**
* Returns a synchronized (thread-safe) list backed by the specified
* list. In order to guarantee serial access, it is critical that
* all access to the backing list is accomplished
* through the returned list.
*
* It is imperative that the user manually synchronize on the returned
* list when iterating over it:
*
* List list = Collections.synchronizedList(new ArrayList());
* ...
* synchronized (list) {
* Iterator i = list.iterator(); // Must be in synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*
* Failure to follow this advice may result in non-deterministic behavior.
*
* The returned list will be serializable if the specified list is
* serializable.
*
* @param list the list to be "wrapped" in a synchronized list.
* @return a synchronized view of the specified list.
*/
public static List synchronizedList(List list) {
return (list instanceof RandomAccess ?
new SynchronizedRandomAccessList<>(list) :
new SynchronizedList<>(list));
}
static List synchronizedList(List list, Object mutex) {
return (list instanceof RandomAccess ?
new SynchronizedRandomAccessList<>(list, mutex) :
new SynchronizedList<>(list, mutex));
}
/**
* @serial include
*/
static class SynchronizedList
extends SynchronizedCollection
implements List {
private static final long serialVersionUID = -7754090372962971524L;
final List list;
SynchronizedList(List list) {
super(list);
this.list = list;
}
SynchronizedList(List list, Object mutex) {
super(list, mutex);
this.list = list;
}
public boolean equals(Object o) {
synchronized (mutex) {return list.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return list.hashCode();}
}
public E get(int index) {
synchronized (mutex) {return list.get(index);}
}
public E set(int index, E element) {
synchronized (mutex) {return list.set(index, element);}
}
public void add(int index, E element) {
synchronized (mutex) {list.add(index, element);}
}
public E remove(int index) {
synchronized (mutex) {return list.remove(index);}
}
public int indexOf(Object o) {
synchronized (mutex) {return list.indexOf(o);}
}
public int lastIndexOf(Object o) {
synchronized (mutex) {return list.lastIndexOf(o);}
}
public boolean addAll(int index, Collection c) {
synchronized (mutex) {return list.addAll(index, c);}
}
public ListIterator listIterator() {
return list.listIterator(); // Must be manually synched by user
}
public ListIterator listIterator(int index) {
return list.listIterator(index); // Must be manually synched by user
}
public List subList(int fromIndex, int toIndex) {
synchronized (mutex) {
return new SynchronizedList<>(list.subList(fromIndex, toIndex),
mutex);
}
}
/**
* SynchronizedRandomAccessList instances are serialized as
* SynchronizedList instances to allow them to be deserialized
* in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
* This method inverts the transformation. As a beneficial
* side-effect, it also grafts the RandomAccess marker onto
* SynchronizedList instances that were serialized in pre-1.4 JREs.
*
* Note: Unfortunately, SynchronizedRandomAccessList instances
* serialized in 1.4.1 and deserialized in 1.4 will become
* SynchronizedList instances, as this method was missing in 1.4.
*/
private Object readResolve() {
return (list instanceof RandomAccess
? new SynchronizedRandomAccessList<>(list)
: this);
}
}
/**
* @serial include
*/
static class SynchronizedRandomAccessList
extends SynchronizedList
implements RandomAccess {
SynchronizedRandomAccessList(List list) {
super(list);
}
SynchronizedRandomAccessList(List list, Object mutex) {
super(list, mutex);
}
public List subList(int fromIndex, int toIndex) {
synchronized (mutex) {
return new SynchronizedRandomAccessList<>(
list.subList(fromIndex, toIndex), mutex);
}
}
private static final long serialVersionUID = 1530674583602358482L;
/**
* Allows instances to be deserialized in pre-1.4 JREs (which do
* not have SynchronizedRandomAccessList). SynchronizedList has
* a readResolve method that inverts this transformation upon
* deserialization.
*/
private Object writeReplace() {
return new SynchronizedList<>(list);
}
}
/**
* Returns a synchronized (thread-safe) map backed by the specified
* map. In order to guarantee serial access, it is critical that
* all access to the backing map is accomplished
* through the returned map.
*
* It is imperative that the user manually synchronize on the returned
* map when iterating over any of its collection views:
*
* Map m = Collections.synchronizedMap(new HashMap());
* ...
* Set s = m.keySet(); // Needn't be in synchronized block
* ...
* synchronized (m) { // Synchronizing on m, not s!
* Iterator i = s.iterator(); // Must be in synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*
* Failure to follow this advice may result in non-deterministic behavior.
*
* The returned map will be serializable if the specified map is
* serializable.
*
* @param m the map to be "wrapped" in a synchronized map.
* @return a synchronized view of the specified map.
*/
public static Map synchronizedMap(Map m) {
return new SynchronizedMap<>(m);
}
/**
* @serial include
*/
private static class SynchronizedMap
implements Map, Serializable {
private static final long serialVersionUID = 1978198479659022715L;
private final Map m; // Backing Map
final Object mutex; // Object on which to synchronize
SynchronizedMap(Map m) {
if (m==null)
throw new NullPointerException();
this.m = m;
mutex = this;
}
SynchronizedMap(Map m, Object mutex) {
this.m = m;
this.mutex = mutex;
}
public int size() {
synchronized (mutex) {return m.size();}
}
public boolean isEmpty() {
synchronized (mutex) {return m.isEmpty();}
}
public boolean containsKey(Object key) {
synchronized (mutex) {return m.containsKey(key);}
}
public boolean containsValue(Object value) {
synchronized (mutex) {return m.containsValue(value);}
}
public V get(Object key) {
synchronized (mutex) {return m.get(key);}
}
public V put(K key, V value) {
synchronized (mutex) {return m.put(key, value);}
}
public V remove(Object key) {
synchronized (mutex) {return m.remove(key);}
}
public void putAll(Map map) {
synchronized (mutex) {m.putAll(map);}
}
public void clear() {
synchronized (mutex) {m.clear();}
}
private transient Set keySet = null;
private transient Set> entrySet = null;
private transient Collection values = null;
public Set keySet() {
synchronized (mutex) {
if (keySet==null)
keySet = new SynchronizedSet<>(m.keySet(), mutex);
return keySet;
}
}
public Set> entrySet() {
synchronized (mutex) {
if (entrySet==null)
entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
return entrySet;
}
}
public Collection values() {
synchronized (mutex) {
if (values==null)
values = new SynchronizedCollection<>(m.values(), mutex);
return values;
}
}
public boolean equals(Object o) {
synchronized (mutex) {return m.equals(o);}
}
public int hashCode() {
synchronized (mutex) {return m.hashCode();}
}
public String toString() {
synchronized (mutex) {return m.toString();}
}
}
/**
* Returns a synchronized (thread-safe) sorted map backed by the specified
* sorted map. In order to guarantee serial access, it is critical that
* all access to the backing sorted map is accomplished
* through the returned sorted map (or its views).
*
* It is imperative that the user manually synchronize on the returned
* sorted map when iterating over any of its collection views, or the
* collections views of any of its subMap, headMap or
* tailMap views.
*
* SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
* ...
* Set s = m.keySet(); // Needn't be in synchronized block
* ...
* synchronized (m) { // Synchronizing on m, not s!
* Iterator i = s.iterator(); // Must be in synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*
* or:
*
* SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
* SortedMap m2 = m.subMap(foo, bar);
* ...
* Set s2 = m2.keySet(); // Needn't be in synchronized block
* ...
* synchronized (m) { // Synchronizing on m, not m2 or s2!
* Iterator i = s.iterator(); // Must be in synchronized block
* while (i.hasNext())
* foo(i.next());
* }
*
* Failure to follow this advice may result in non-deterministic behavior.
*
* The returned sorted map will be serializable if the specified
* sorted map is serializable.
*
* @param m the sorted map to be "wrapped" in a synchronized sorted map.
* @return a synchronized view of the specified sorted map.
*/
public static SortedMap synchronizedSortedMap(SortedMap m) {
return new SynchronizedSortedMap<>(m);
}
/**
* @serial include
*/
static class SynchronizedSortedMap
extends SynchronizedMap
implements SortedMap
{
private static final long serialVersionUID = -8798146769416483793L;
private final SortedMap sm;
SynchronizedSortedMap(SortedMap m) {
super(m);
sm = m;
}
SynchronizedSortedMap(SortedMap m, Object mutex) {
super(m, mutex);
sm = m;
}
public Comparator comparator() {
synchronized (mutex) {return sm.comparator();}
}
public SortedMap subMap(K fromKey, K toKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(
sm.subMap(fromKey, toKey), mutex);
}
}
public SortedMap headMap(K toKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex);
}
}
public SortedMap tailMap(K fromKey) {
synchronized (mutex) {
return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex);
}
}
public K firstKey() {
synchronized (mutex) {return sm.firstKey();}
}
public K lastKey() {
synchronized (mutex) {return sm.lastKey();}
}
}
// Dynamically typesafe collection wrappers
/**
* Returns a dynamically typesafe view of the specified collection.
* Any attempt to insert an element of the wrong type will result in an
* immediate {@link ClassCastException}. Assuming a collection
* contains no incorrectly typed elements prior to the time a
* dynamically typesafe view is generated, and that all subsequent
* access to the collection takes place through the view, it is
* guaranteed that the collection cannot contain an incorrectly
* typed element.
*
* The generics mechanism in the language provides compile-time
* (static) type checking, but it is possible to defeat this mechanism
* with unchecked casts. Usually this is not a problem, as the compiler
* issues warnings on all such unchecked operations. There are, however,
* times when static type checking alone is not sufficient. For example,
* suppose a collection is passed to a third-party library and it is
* imperative that the library code not corrupt the collection by
* inserting an element of the wrong type.
*
*
Another use of dynamically typesafe views is debugging. Suppose a
* program fails with a {@code ClassCastException}, indicating that an
* incorrectly typed element was put into a parameterized collection.
* Unfortunately, the exception can occur at any time after the erroneous
* element is inserted, so it typically provides little or no information
* as to the real source of the problem. If the problem is reproducible,
* one can quickly determine its source by temporarily modifying the
* program to wrap the collection with a dynamically typesafe view.
* For example, this declaration:
*
{@code
* Collection c = new HashSet();
* }
* may be replaced temporarily by this one:
* {@code
* Collection c = Collections.checkedCollection(
* new HashSet(), String.class);
* }
* Running the program again will cause it to fail at the point where
* an incorrectly typed element is inserted into the collection, clearly
* identifying the source of the problem. Once the problem is fixed, the
* modified declaration may be reverted back to the original.
*
* The returned collection does not pass the hashCode and equals
* operations through to the backing collection, but relies on
* {@code Object}'s {@code equals} and {@code hashCode} methods. This
* is necessary to preserve the contracts of these operations in the case
* that the backing collection is a set or a list.
*
*
The returned collection will be serializable if the specified
* collection is serializable.
*
*
Since {@code null} is considered to be a value of any reference
* type, the returned collection permits insertion of null elements
* whenever the backing collection does.
*
* @param c the collection for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code c} is permitted to hold
* @return a dynamically typesafe view of the specified collection
* @since 1.5
*/
public static Collection checkedCollection(Collection c,
Class type) {
return new CheckedCollection<>(c, type);
}
@SuppressWarnings("unchecked")
static T[] zeroLengthArray(Class type) {
return (T[]) Array.newInstance(type, 0);
}
/**
* @serial include
*/
static class CheckedCollection implements Collection, Serializable {
private static final long serialVersionUID = 1578914078182001775L;
final Collection c;
final Class type;
void typeCheck(Object o) {
if (o != null && !type.isInstance(o))
throw new ClassCastException(badElementMsg(o));
}
private String badElementMsg(Object o) {
return "Attempt to insert " + o.getClass() +
" element into collection with element type " + type;
}
CheckedCollection(Collection c, Class type) {
if (c==null || type == null)
throw new NullPointerException();
this.c = c;
this.type = type;
}
public int size() { return c.size(); }
public boolean isEmpty() { return c.isEmpty(); }
public boolean contains(Object o) { return c.contains(o); }
public Object[] toArray() { return c.toArray(); }
public T[] toArray(T[] a) { return c.toArray(a); }
public String toString() { return c.toString(); }
public boolean remove(Object o) { return c.remove(o); }
public void clear() { c.clear(); }
public boolean containsAll(Collection coll) {
return c.containsAll(coll);
}
public boolean removeAll(Collection coll) {
return c.removeAll(coll);
}
public boolean retainAll(Collection coll) {
return c.retainAll(coll);
}
public Iterator iterator() {
final Iterator it = c.iterator();
return new Iterator() {
public boolean hasNext() { return it.hasNext(); }
public E next() { return it.next(); }
public void remove() { it.remove(); }};
}
public boolean add(E e) {
typeCheck(e);
return c.add(e);
}
private E[] zeroLengthElementArray = null; // Lazily initialized
private E[] zeroLengthElementArray() {
return zeroLengthElementArray != null ? zeroLengthElementArray :
(zeroLengthElementArray = zeroLengthArray(type));
}
@SuppressWarnings("unchecked")
Collection checkedCopyOf(Collection coll) {
Object[] a = null;
try {
E[] z = zeroLengthElementArray();
a = coll.toArray(z);
// Defend against coll violating the toArray contract
if (a.getClass() != z.getClass())
a = Arrays.copyOf(a, a.length, z.getClass());
} catch (ArrayStoreException ignore) {
// To get better and consistent diagnostics,
// we call typeCheck explicitly on each element.
// We call clone() to defend against coll retaining a
// reference to the returned array and storing a bad
// element into it after it has been type checked.
a = coll.toArray().clone();
for (Object o : a)
typeCheck(o);
}
// A slight abuse of the type system, but safe here.
return (Collection) Arrays.asList(a);
}
public boolean addAll(Collection coll) {
// Doing things this way insulates us from concurrent changes
// in the contents of coll and provides all-or-nothing
// semantics (which we wouldn't get if we type-checked each
// element as we added it)
return c.addAll(checkedCopyOf(coll));
}
}
/**
* Returns a dynamically typesafe view of the specified set.
* Any attempt to insert an element of the wrong type will result in
* an immediate {@link ClassCastException}. Assuming a set contains
* no incorrectly typed elements prior to the time a dynamically typesafe
* view is generated, and that all subsequent access to the set
* takes place through the view, it is guaranteed that the
* set cannot contain an incorrectly typed element.
*
* A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link #checkedCollection
* checkedCollection} method.
*
*
The returned set will be serializable if the specified set is
* serializable.
*
*
Since {@code null} is considered to be a value of any reference
* type, the returned set permits insertion of null elements whenever
* the backing set does.
*
* @param s the set for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code s} is permitted to hold
* @return a dynamically typesafe view of the specified set
* @since 1.5
*/
public static Set checkedSet(Set s, Class type) {
return new CheckedSet<>(s, type);
}
/**
* @serial include
*/
static class CheckedSet extends CheckedCollection
implements Set, Serializable
{
private static final long serialVersionUID = 4694047833775013803L;
CheckedSet(Set s, Class elementType) { super(s, elementType); }
public boolean equals(Object o) { return o == this || c.equals(o); }
public int hashCode() { return c.hashCode(); }
}
/**
* Returns a dynamically typesafe view of the specified sorted set.
* Any attempt to insert an element of the wrong type will result in an
* immediate {@link ClassCastException}. Assuming a sorted set
* contains no incorrectly typed elements prior to the time a
* dynamically typesafe view is generated, and that all subsequent
* access to the sorted set takes place through the view, it is
* guaranteed that the sorted set cannot contain an incorrectly
* typed element.
*
* A discussion of the use of dynamically typesafe views may be
* found in the documentation for the {@link #checkedCollection
* checkedCollection} method.
*
*
The returned sorted set will be serializable if the specified sorted
* set is serializable.
*
*
Since {@code null} is considered to be a value of any reference
* type, the returned sorted set permits insertion of null elements
* whenever the backing sorted set does.
*
* @param s the sorted set for which a dynamically typesafe view is to be
* returned
* @param type the type of element that {@code s} is permitted to hold
* @return a dynamically typesafe view of the specified sorted set
* @since 1.5
*/
public static SortedSet checkedSortedSet(SortedSet s,
Class type) {
return new CheckedSortedSet<>(s, type);
}
/**
* @serial include
*/
static class CheckedSortedSet extends CheckedSet