marcel.lang.primitives.iterators.IntIterators Maven / Gradle / Ivy
package marcel.lang.primitives.iterators;
import marcel.lang.primitives.iterators.list.IntListIterator;
import marcel.lang.util.Arrays;
import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.PrimitiveIterator;
import java.util.function.Consumer;
public final class IntIterators {
private IntIterators() {}
/** A class returning no elements and a type-specific iterator interface.
*
* This class may be useful to implement your own in case you subclass
* a type-specific iterator.
*/
public static class EmptyIterator implements IntListIterator, java.io.Serializable, Cloneable {
private static final long serialVersionUID = -7046029254386353129L;
protected EmptyIterator() {}
@Override
public boolean hasNext() { return false; }
@Override
public boolean hasPrevious() { return false; }
@Override
public int nextInt() { throw new NoSuchElementException(); }
@Override
public int previousInt() { throw new NoSuchElementException(); }
@Override
public int nextIndex() { return 0; }
@Override
public int previousIndex() { return -1; }
@Override
public int skip(int n) { return 0; }
//@Override
public int back(int n) { return 0; }
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) { }
@Deprecated
@Override
public void forEachRemaining(final Consumer action) { }
@Override
public Object clone() { return EMPTY_ITERATOR; }
private Object readResolve() { return EMPTY_ITERATOR; }
}
/** An empty iterator. It is serializable and cloneable.
*
*
The class of this objects represent an abstract empty iterator
* that can iterate as a type-specific (list) iterator.
*/
public static final EmptyIterator EMPTY_ITERATOR = new EmptyIterator();
/** An iterator returning a single element. */
private static class SingletonIterator implements IntListIterator {
private final int element;
private byte curr;
public SingletonIterator(final int element) {
this.element = element;
}
@Override
public boolean hasNext() { return curr == 0; }
@Override
public boolean hasPrevious() { return curr == 1; }
@Override
public int nextInt() {
if (! hasNext()) throw new NoSuchElementException();
curr = 1;
return element;
}
@Override
public int previousInt() {
if (! hasPrevious()) throw new NoSuchElementException();
curr = 0;
return element;
}
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
Objects.requireNonNull(action);
if (curr == 0) {
action.accept(element);
curr = 1;
}
}
@Override
public int nextIndex() {
return curr;
}
@Override
public int previousIndex() {
return curr - 1;
}
// @Override
public int back(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
if (n == 0 || curr < 1) return 0;
curr = 1;
return 1;
}
@Override
public int skip(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
if (n == 0 || curr > 0) return 0;
curr = 0;
return 1;
}
}
/** Returns an immutable iterator that iterates just over the given element.
*
* @param element the only element to be returned by a type-specific list iterator.
* @return an immutable iterator that iterates just over {@code element}.
*/
public static IntListIterator singleton(final int element) {
return new SingletonIterator (element);
}
/** A class to wrap arrays in iterators. */
private static class ArrayIterator implements IntListIterator {
private final int[] array;
private final int offset, length;
private int curr;
public ArrayIterator(final int[] array, final int offset, final int length) {
this.array = array;
this.offset = offset;
this.length = length;
}
@Override
public boolean hasNext() { return curr < length; }
@Override
public boolean hasPrevious() { return curr > 0; }
@Override
public int nextInt() {
if (! hasNext()) throw new NoSuchElementException();
return array[offset + curr++];
}
@Override
public int previousInt() {
if (! hasPrevious()) throw new NoSuchElementException();
return array[offset + --curr];
}
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
Objects.requireNonNull(action);
for (; curr < length; ++curr) {
action.accept(array[offset + curr]);
}
}
@Override
public int skip(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
if (n <= length - curr) {
curr += n;
return n;
}
n = length - curr;
curr = length;
return n;
}
//@Override
public int back(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
if (n <= curr) {
curr -= n;
return n;
}
n = curr;
curr = 0;
return n;
}
@Override
public int nextIndex() {
return curr;
}
@Override
public int previousIndex() {
return curr - 1;
}
}
/** Wraps the given part of an array into a type-specific list iterator.
*
*
The type-specific list iterator returned by this method will iterate
* {@code length} times, returning consecutive elements of the given
* array starting from the one with index {@code offset}.
*
* @param array an array to wrap into a type-specific list iterator.
* @param offset the first element of the array to be returned.
* @param length the number of elements to return.
* @return an iterator that will return {@code length} elements of {@code array} starting at position {@code offset}.
*/
public static IntListIterator wrap(final int[] array, final int offset, final int length) {
Arrays.ensureOffsetLength(array, offset, length);
return new ArrayIterator (array, offset, length);
}
/** Wraps the given array into a type-specific list iterator.
*
*
The type-specific list iterator returned by this method will return
* all elements of the given array.
*
* @param array an array to wrap into a type-specific list iterator.
* @return an iterator that will return the elements of {@code array}.
*/
public static IntListIterator wrap(final int[] array) {
return new ArrayIterator (array, 0, array.length);
}
/** Unwraps an iterator into an array starting at a given offset for a given number of elements.
*
*
This method iterates over the given type-specific iterator and stores the elements
* returned, up to a maximum of {@code length}, in the given array starting at {@code offset}.
* The number of actually unwrapped elements is returned (it may be less than {@code max} if
* the iterator emits less than {@code max} elements).
*
* @param i a type-specific iterator.
* @param array an array to contain the output of the iterator.
* @param offset the first element of the array to be returned.
* @param max the maximum number of elements to unwrap.
* @return the number of elements unwrapped.
*/
public static int unwrap(final IntIterator i, final int array[], int offset, final int max) {
if (max < 0) throw new IllegalArgumentException("The maximum number of elements (" + max + ") is negative");
if (offset < 0 || offset + max > array.length) throw new IllegalArgumentException();
int j = max;
while(j-- != 0 && i.hasNext()) array[offset++] = i.nextInt();
return max - j - 1;
}
private static class IteratorWrapper implements IntIterator {
final Iterator i;
public IteratorWrapper(final Iterator i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public void remove() { i.remove(); }
@Override
public int nextInt() { return (i.next()).intValue(); }
@SuppressWarnings("unchecked")
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
Objects.requireNonNull(action);
i.forEachRemaining(action instanceof Consumer ? (Consumer)action : action::accept);
}
@Deprecated
@Override
public void forEachRemaining(final Consumer action) {
i.forEachRemaining(action);
}
}
private static class PrimitiveIteratorWrapper implements IntIterator {
final PrimitiveIterator.OfInt i;
public PrimitiveIteratorWrapper(PrimitiveIterator.OfInt i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public void remove() { i.remove(); }
@Override
public int nextInt() { return i.nextInt(); }
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
i.forEachRemaining(action);
}
}
/** Wraps a standard iterator into a type-specific iterator.
*
* This method wraps a standard iterator into a type-specific one which will handle the
* type conversions for you. Of course, any attempt to wrap an iterator returning the
* instances of the wrong class will generate a {@link ClassCastException}. The
* returned iterator is backed by {@code i}: changes to one of the iterators
* will affect the other, too.
*
* If {@code i} is already type-specific, it will returned and no new object
* will be generated.
*
* @param i an iterator.
* @return a type-specific iterator backed by {@code i}.
*/
@SuppressWarnings({"unchecked","rawtypes"})
public static IntIterator asIntIterator(final Iterator i) {
if (i instanceof IntIterator) return (IntIterator )i;
if (i instanceof PrimitiveIterator.OfInt) return new PrimitiveIteratorWrapper ((PrimitiveIterator.OfInt)i);
return new IteratorWrapper (i);
}
private static class ListIteratorWrapper implements IntListIterator {
final ListIterator i;
public ListIteratorWrapper(final ListIterator i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public boolean hasPrevious() { return i.hasPrevious(); }
@Override
public int nextIndex() { return i.nextIndex(); }
@Override
public int previousIndex() { return i.previousIndex(); }
@Override
public void set(int k) { i.set(Integer.valueOf(k)); }
@Override
public void add(int k) { i.add(Integer.valueOf(k)); }
@Override
public void remove() { i.remove(); }
@Override
public int nextInt() { return (i.next()).intValue(); }
@Override
public int previousInt() { return (i.previous()).intValue(); }
@SuppressWarnings("unchecked")
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
Objects.requireNonNull(action);
i.forEachRemaining(action instanceof Consumer ? (Consumer)action : action::accept);
}
@Deprecated
@Override
public void forEachRemaining(final Consumer action) {
i.forEachRemaining(action);
}
}
/** Wraps a standard list iterator into a type-specific list iterator.
*
* This method wraps a standard list iterator into a type-specific one
* which will handle the type conversions for you. Of course, any attempt
* to wrap an iterator returning the instances of the wrong class will
* generate a {@link ClassCastException}. The
* returned iterator is backed by {@code i}: changes to one of the iterators
* will affect the other, too.
*
*
If {@code i} is already type-specific, it will returned and no new object
* will be generated.
*
* @param i a list iterator.
* @return a type-specific list iterator backed by {@code i}.
*/
@SuppressWarnings({"unchecked","rawtypes"})
public static IntListIterator asIntIterator(final ListIterator i) {
if (i instanceof IntListIterator) return (IntListIterator )i;
return new ListIteratorWrapper (i);
}
/**
* Returns whether an element returned by the given iterator satisfies the given predicate.
*
Short circuit evaluation is performed; the first {@code true} from the predicate terminates the loop.
* @return true if an element returned by {@code iterator} satisfies {@code predicate}.
*/
public static boolean any(final IntIterator iterator, final java.util.function.IntPredicate predicate) {
return indexOf(iterator, predicate) != -1;
}
/**
* Returns whether all elements returned by the given iterator satisfy the given predicate.
*
Short circuit evaluation is performed; the first {@code false} from the predicate terminates the loop.
* @return true if all elements returned by {@code iterator} satisfy {@code predicate}.
*/
public static boolean all(final IntIterator iterator, final java.util.function.IntPredicate predicate) {
Objects.requireNonNull(predicate);
do {
if (!iterator.hasNext()) return true;
} while (predicate.test(iterator.nextInt()));
return false;
}
/**
* Returns the index of the first element returned by the given iterator that satisfies the given predicate, or −1 if
* no such element was found.
*
The next element returned by the iterator always considered element 0, even for
* {@link java.util.ListIterator ListIterators}. In other words {@link java.util.ListIterator#nextIndex
* ListIterator.nextIndex} is ignored.
* @return the index of the first element returned by {@code iterator} that satisfies {@code predicate}, or −1 if
* no such element was found.
*/
public static int indexOf(final IntIterator iterator, final java.util.function.IntPredicate predicate) {
Objects.requireNonNull(predicate);
for (int i = 0; iterator.hasNext(); ++i) {
if (predicate.test(iterator.nextInt())) return i;
}
return -1;
}
/**
* A skeletal implementation for an iterator backed by an index-based data store. High performance
* concrete implementations (like the main Iterator of ArrayList) generally should avoid using this
* and just implement the interface directly, but should be decent for less
* performance critical implementations.
*
*
This class is only appropriate for sequences that are at most {@link Integer#MAX_VALUE} long.
* If your backing data store can be bigger then this, consider the equivalently named class in
* the type specific {@code BigListIterators} class.
*
*
As the abstract methods in this class are used in inner loops, it is generally a
* good idea to override the class as {@code final} as to encourage the JVM to inline
* them (or alternatively, override the abstract methods as final).
*/
public static abstract class AbstractIndexBasedIterator extends AbstractIntIterator {
/** The minimum pos can be, and is the logical start of the "range".
* Usually set to the initialPos unless it is a ListIterator, in which case it can vary.
*
* There isn't any way for a range to shift its beginning like the end can (through {@link #remove}),
* so this is final.
*/
protected final int minPos;
/** The current position index, the index of the item to be returned after the next call to {@link #next()}.
*
*
This value will be between {@code minPos} and {@link #getMaxPos()} (exclusive) (on a best effort, so concurrent
* structural modifications outside this iterator may cause this to be violated, but that usually invalidates
* iterators anyways). Thus {@code pos} being {@code minPos + 2} would mean {@link #next()}
* was called twice and the next call will return the third element of this iterator.
*/
protected int pos;
/** The last returned index by a call to {@link #next} or, if a list-iterator, {@link java.util.ListIterator#previous()}.
*
* It is −1 if no such call has occurred or a mutation has occurred through this iterator and no
* advancement has been done.
*/
protected int lastReturned;
protected AbstractIndexBasedIterator(int minPos, int initialPos) {
this.minPos = minPos;
this.pos = initialPos;
}
// When you implement these, you should probably declare them final to encourage the JVM to inline them.
/** Get the item corresponding to the given index location.
*
*
Do not advance {@link #pos} in this method; the default {@code next} method takes care of this.
*
*
The {@code location} given will be between {@code minPos} and {@link #getMaxPos()} (exclusive).
* Thus, a {@code location} of {@code minPos + 2} would mean {@link #next()} was called twice
* and this method should return what the next call to {@link #next()} should return.
*/
protected abstract int get(int location);
/** Remove the item at the given index.
*
*
Do not modify {@link #pos} in this method; the default {@code #remove()} method takes care of this.
*
*
This method should also do what is needed to track the change to the {@link #getMaxPos}.
* Usually this is accomplished by having this method call the parent Collection's appropriate remove
* method, and having {@link #getMaxPos} track the parent Collection#size().
*/
protected abstract void remove(int location);
/** The maximum pos can be, and is the logical end (exclusive) of the "range".
*
*
If pos is equal to the return of this method, this means the last element has been returned and the next call to {@link #next()} will throw.
*
*
Usually set return the parent Collection#size(), but does not have to be
* (for example, sublists and subranges).
*/
protected abstract int getMaxPos();
@Override
public boolean hasNext() { return pos < getMaxPos(); }
@Override
public int nextInt() { if (! hasNext()) throw new NoSuchElementException(); return get(lastReturned = pos++); }
@Override
public void remove() {
if (lastReturned == -1) throw new IllegalStateException();
remove(lastReturned);
/* If the last operation was a next(), we are removing an element *before* us, and we must decrease pos correspondingly. */
if (lastReturned < pos) pos--;
lastReturned = -1;
}
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
while(pos < getMaxPos()) {
action.accept(get(lastReturned = pos++));
}
}
@Override
public int skip(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
final int max = getMaxPos();
final int remaining = max - pos;
if (n < remaining) {
pos += n;
} else {
n = remaining;
pos = max;
}
lastReturned = pos - 1;
return n;
}
}
/**
* A skeletal implementation for a list-iterator backed by an index-based data store. High performance
* concrete implementations (like the main ListIterator of ArrayList) generally should avoid using this
* and just implement the interface directly, but should be decent for less
* performance critical implementations.
*
*
This class is only appropriate for sequences that are at most {@link Integer#MAX_VALUE} long.
* If your backing data store can be bigger then this, consider the equivalently named class in
* the type specific {@code BigListSpliterators} class.
*
*
As the abstract methods in this class are used in inner loops, it is generally a
* good idea to override the class as {@code final} as to encourage the JVM to inline
* them (or alternatively, override the abstract methods as final).
*/
public static abstract class AbstractIndexBasedListIterator extends AbstractIndexBasedIterator implements IntListIterator {
protected AbstractIndexBasedListIterator(int minPos, int initialPos) {
super(minPos, initialPos);
}
// When you implement these, you should probably declare them final to encourage the JVM to inline them.
/** Add the given item at the given index.
*
*
This method should also do what is needed to track the change to the {@link #getMaxPos}.
* Usually this is accomplished by having this method call the parent Collection's appropriate add
* method, and having {@link #getMaxPos} track the parent Collection#size().
*
*
Do not modify {@link #pos} in this method; the default {@code #add()} method takes care of this.
*
*
See {@link #pos} and {@link #get(int)} for discussion on what the location means.
*/
protected abstract void add(int location, int k);
/** Sets the given item at the given index.
*
*
See {@link #pos} and {@link #get(int)} for discussion on what the location means.
*/
protected abstract void set(int location, int k);
@Override
public boolean hasPrevious() { return pos > minPos; }
@Override
public int previousInt() { if (! hasPrevious()) throw new NoSuchElementException(); return get(lastReturned = --pos); }
@Override
public int nextIndex() { return pos; }
@Override
public int previousIndex() { return pos - 1; }
@Override
public void add(final int k) {
add(pos++, k);
lastReturned = -1;
}
@Override
public void set(final int k) {
if (lastReturned == -1) throw new IllegalStateException();
set(lastReturned, k);
}
// @Override
public int back(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
final int remaining = pos - minPos;
if (n < remaining) {
pos -= n;
} else {
n = remaining;
pos = minPos;
}
lastReturned = pos;
return n;
}
}
private static class IntervalIterator implements IntListIterator {
private final int from, to;
int curr;
public IntervalIterator(final int from, final int to) {
this.from = this.curr = from;
this.to = to;
}
@Override
public boolean hasNext() { return curr < to; }
@Override
public boolean hasPrevious() { return curr > from; }
@Override
public int nextInt() {
if (! hasNext()) throw new NoSuchElementException();
return curr++;
}
@Override
public int previousInt() {
if (! hasPrevious()) throw new NoSuchElementException();
return --curr;
}
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
Objects.requireNonNull(action);
for (; curr < to; ++curr) {
action.accept(curr);
}
}
@Override
public int nextIndex() { return curr - from; }
@Override
public int previousIndex() { return curr - from - 1; }
@Override
public int skip(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
if (curr + n <= to) {
curr += n;
return n;
}
n = to - curr;
curr = to;
return n;
}
//@Override
public int back(int n) {
if (curr - n >= from) {
curr -= n;
return n;
}
n = curr - from ;
curr = from;
return n;
}
}
/** Creates a type-specific list iterator over an interval.
*
*
The type-specific list iterator returned by this method will return the
* elements {@code from}, {@code from+1},…, {@code to-1}.
*
* @param from the starting element (inclusive).
* @param to the ending element (exclusive).
* @return a type-specific list iterator enumerating the elements from {@code from} to {@code to}.
*/
public static IntListIterator fromTo(final int from, final int to) {
return new IntervalIterator(from, to);
}
private static class IteratorConcatenator implements IntIterator {
final IntIterator a[];
int offset, length, lastOffset = -1;
public IteratorConcatenator(final IntIterator a[], int offset, int length) {
this.a = a;
this.offset = offset;
this.length = length;
advance();
}
private void advance() {
while(length != 0) {
if (a[offset].hasNext()) break;
length--;
offset++;
}
return;
}
@Override
public boolean hasNext() {
return length > 0;
}
@Override
public int nextInt() {
if (! hasNext()) throw new NoSuchElementException();
int next = a[lastOffset = offset].nextInt();
advance();
return next;
}
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
while (length > 0) {
a[lastOffset = offset].forEachRemaining(action);
advance();
}
}
@Deprecated
@Override
public void forEachRemaining(final Consumer action) {
while (length > 0) {
a[lastOffset = offset].forEachRemaining(action);
advance();
}
}
@Override
public void remove() {
if (lastOffset == -1) throw new IllegalStateException();
a[lastOffset].remove();
}
@Override
public int skip(int n) {
if (n < 0) throw new IllegalArgumentException("Argument must be nonnegative: " + n);
lastOffset = -1;
int skipped = 0;
while(skipped < n && length != 0) {
skipped += a[offset].skip(n - skipped);
if (a[offset].hasNext()) break;
length--;
offset++;
}
return skipped;
}
}
/** Concatenates all iterators contained in an array.
*
*
This method returns an iterator that will enumerate in order the elements returned
* by all iterators contained in the given array.
*
* @param a an array of iterators.
* @return an iterator obtained by concatenation.
*/
public static IntIterator concat(final IntIterator ... a) {
return concat(a, 0, a.length);
}
/** Concatenates a sequence of iterators contained in an array.
*
*
This method returns an iterator that will enumerate in order the elements returned
* by {@code a[offset]}, then those returned
* by {@code a[offset + 1]}, and so on up to
* {@code a[offset + length - 1]}.
*
* @param a an array of iterators.
* @param offset the index of the first iterator to concatenate.
* @param length the number of iterators to concatenate.
* @return an iterator obtained by concatenation of {@code length} elements of {@code a} starting at {@code offset}.
*/
public static IntIterator concat(final IntIterator a[], final int offset, final int length) {
return new IteratorConcatenator (a, offset, length);
}
/** An unmodifiable wrapper class for iterators. */
public static class UnmodifiableIterator implements IntIterator {
protected final IntIterator i;
public UnmodifiableIterator(final IntIterator i) {
this.i = i;
}
@Override
public boolean hasNext() { return i.hasNext(); }
@Override
public int nextInt() { return i.nextInt(); }
@Override
public void forEachRemaining(final java.util.function.IntConsumer action) {
i.forEachRemaining(action);
}
@Deprecated
@Override
public void forEachRemaining(final Consumer action) {
i.forEachRemaining(action);
}
}
}