com.twelvemonkeys.util.CollectionUtil Maven / Gradle / Ivy
/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name "TwelveMonkeys" nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.twelvemonkeys.util;
import java.lang.reflect.Array;
import java.util.*;
/**
* A utility class with some useful collection-related functions.
*
* @author Harald Kuhr
* @author Eirik Torske
* @author last modified by $Author: haku $
* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/CollectionUtil.java#3 $
* @todo move makeList and makeSet to StringUtil?
* @see Collections
* @see Arrays
*/
public final class CollectionUtil {
/**
* Testing only.
*
* @param pArgs command line arguents
*/
@SuppressWarnings({"UnusedDeclaration", "UnusedAssignment", "unchecked"})
public static void main(String[] pArgs) {
test();
int howMany = 1000;
if (pArgs.length > 0) {
howMany = Integer.parseInt(pArgs[0]);
}
long start;
long end;
/*
int[] intArr1 = new int[] {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
};
int[] intArr2 = new int[] {
10, 11, 12, 13, 14, 15, 16, 17, 18, 19
};
start = System.currentTimeMillis();
for (int i = 0; i < howMany; i++) {
intArr1 = (int[]) mergeArrays(intArr1, 0, intArr1.length, intArr2, 0, intArr2.length);
}
end = System.currentTimeMillis();
System.out.println("mergeArrays: " + howMany + " * " + intArr2.length + " ints took " + (end - start) + " milliseconds (" + intArr1.length
+ ")");
*/
////////////////////////////////
String[] stringArr1 = new String[]{
"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"
};
/*
String[] stringArr2 = new String[] {
"ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"
};
start = System.currentTimeMillis();
for (int i = 0; i < howMany; i++) {
stringArr1 = (String[]) mergeArrays(stringArr1, 0, stringArr1.length, stringArr2, 0, stringArr2.length);
}
end = System.currentTimeMillis();
System.out.println("mergeArrays: " + howMany + " * " + stringArr2.length + " Strings took " + (end - start) + " milliseconds ("
+ stringArr1.length + ")");
start = System.currentTimeMillis();
while (intArr1.length > stringArr2.length) {
intArr1 = (int[]) subArray(intArr1, 0, intArr1.length - stringArr2.length);
}
end = System.currentTimeMillis();
System.out.println("subArray: " + howMany + " * " + intArr2.length + " ints took " + (end - start) + " milliseconds (" + intArr1.length
+ ")");
start = System.currentTimeMillis();
while (stringArr1.length > stringArr2.length) {
stringArr1 = (String[]) subArray(stringArr1, stringArr2.length);
}
end = System.currentTimeMillis();
System.out.println("subArray: " + howMany + " * " + stringArr2.length + " Strings took " + (end - start) + " milliseconds ("
+ stringArr1.length + ")");
*/
stringArr1 = new String[]{
"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen",
"fifteen", "sixteen", "seventeen", "eighteen", "nineteen"
};
System.out.println("\nFilterIterators:\n");
List list = Arrays.asList(stringArr1);
Iterator iter = new FilterIterator(list.iterator(), new FilterIterator.Filter() {
public boolean accept(Object pElement) {
return ((String) pElement).length() > 5;
}
});
while (iter.hasNext()) {
String str = (String) iter.next();
System.out.println(str + " has more than 5 letters!");
}
iter = new FilterIterator(list.iterator(), new FilterIterator.Filter() {
public boolean accept(Object pElement) {
return ((String) pElement).length() <= 5;
}
});
while (iter.hasNext()) {
String str = (String) iter.next();
System.out.println(str + " has less than, or exactly 5 letters!");
}
start = System.currentTimeMillis();
for (int i = 0; i < howMany; i++) {
iter = new FilterIterator(list.iterator(), new FilterIterator.Filter() {
public boolean accept(Object pElement) {
return ((String) pElement).length() <= 5;
}
});
while (iter.hasNext()) {
iter.next();
System.out.print("");
}
}
// end = System.currentTimeMillis();
// System.out.println("Time: " + (end - start) + " ms");
// System.out.println("\nClosureCollection:\n");
// forEach(list, new Closure() {
//
// public void execute(Object pElement) {
//
// String str = (String) pElement;
//
// if (str.length() > 5) {
// System.out.println(str + " has more than 5 letters!");
// }
// else {
// System.out.println(str + " has less than, or exactly 5 letters!");
// }
// }
// });
// start = System.currentTimeMillis();
// for (int i = 0; i < howMany; i++) {
// forEach(list, new Closure() {
//
// public void execute(Object pElement) {
//
// String str = (String) pElement;
//
// if (str.length() <= 5) {
// System.out.print("");
// }
// }
// });
// }
// end = System.currentTimeMillis();
// System.out.println("Time: " + (end - start) + " ms");
}
// Disallow creating objects of this type
private CollectionUtil() {}
/**
* Merges two arrays into a new array. Elements from array1 and array2 will
* be copied into a new array, that has array1.length + array2.length
* elements.
*
* @param pArray1 First array
* @param pArray2 Second array, must be compatible with (assignable from)
* the first array
* @return A new array, containing the values of array1 and array2. The
* array (wrapped as an object), will have the length of array1 +
* array2, and can be safely cast to the type of the array1
* parameter.
* @see #mergeArrays(Object,int,int,Object,int,int)
* @see java.lang.System#arraycopy(Object,int,Object,int,int)
*/
public static Object mergeArrays(Object pArray1, Object pArray2) {
return mergeArrays(pArray1, 0, Array.getLength(pArray1), pArray2, 0, Array.getLength(pArray2));
}
/**
* Merges two arrays into a new array. Elements from pArray1 and pArray2 will
* be copied into a new array, that has pLength1 + pLength2 elements.
*
* @param pArray1 First array
* @param pOffset1 the offset into the first array
* @param pLength1 the number of elements to copy from the first array
* @param pArray2 Second array, must be compatible with (assignable from)
* the first array
* @param pOffset2 the offset into the second array
* @param pLength2 the number of elements to copy from the second array
* @return A new array, containing the values of pArray1 and pArray2. The
* array (wrapped as an object), will have the length of pArray1 +
* pArray2, and can be safely cast to the type of the pArray1
* parameter.
* @see java.lang.System#arraycopy(Object,int,Object,int,int)
*/
@SuppressWarnings({"SuspiciousSystemArraycopy"})
public static Object mergeArrays(Object pArray1, int pOffset1, int pLength1, Object pArray2, int pOffset2, int pLength2) {
Class class1 = pArray1.getClass();
Class type = class1.getComponentType();
// Create new array of the new length
Object array = Array.newInstance(type, pLength1 + pLength2);
System.arraycopy(pArray1, pOffset1, array, 0, pLength1);
System.arraycopy(pArray2, pOffset2, array, pLength1, pLength2);
return array;
}
/**
* Creates an array containing a subset of the original array.
* If the sub array is same length as the original
* ({@code pStart == 0}), the original array will be returned.
*
* @param pArray the origianl array
* @param pStart the start index of the original array
* @return a subset of the original array, or the original array itself,
* if {@code pStart} is 0.
*
* @throws IllegalArgumentException if {@code pArray} is {@code null} or
* if {@code pArray} is not an array.
* @throws ArrayIndexOutOfBoundsException if {@code pStart} < 0
*/
public static Object subArray(Object pArray, int pStart) {
return subArray(pArray, pStart, -1);
}
/**
* Creates an array containing a subset of the original array.
* If the {@code pLength} parameter is negative, it will be ignored.
* If there are not {@code pLength} elements in the original array
* after {@code pStart}, the {@code pLength} paramter will be
* ignored.
* If the sub array is same length as the original, the original array will
* be returned.
*
* @param pArray the origianl array
* @param pStart the start index of the original array
* @param pLength the length of the new array
* @return a subset of the original array, or the original array itself,
* if {@code pStart} is 0 and {@code pLength} is either
* negative, or greater or equal to {@code pArray.length}.
*
* @throws IllegalArgumentException if {@code pArray} is {@code null} or
* if {@code pArray} is not an array.
* @throws ArrayIndexOutOfBoundsException if {@code pStart} < 0
*/
@SuppressWarnings({"SuspiciousSystemArraycopy"})
public static Object subArray(Object pArray, int pStart, int pLength) {
if (pArray == null) {
throw new IllegalArgumentException("array == null");
}
// Get component type
Class type;
// Sanity check start index
if (pStart < 0) {
throw new ArrayIndexOutOfBoundsException(pStart + " < 0");
}
// Check if argument is array
else if ((type = pArray.getClass().getComponentType()) == null) {
// NOTE: No need to test class.isArray(), really
throw new IllegalArgumentException("Not an array: " + pArray);
}
// Store original length
int originalLength = Array.getLength(pArray);
// Find new length, stay within bounds
int newLength = (pLength < 0)
? Math.max(0, originalLength - pStart)
: Math.min(pLength, Math.max(0, originalLength - pStart));
// Store result
Object result;
if (newLength < originalLength) {
// Create subarray & copy into
result = Array.newInstance(type, newLength);
System.arraycopy(pArray, pStart, result, 0, newLength);
}
else {
// Just return original array
// NOTE: This can ONLY happen if pStart == 0
result = pArray;
}
// Return
return result;
}
public static Iterator iterator(final Enumeration pEnum) {
return new Iterator() {
public boolean hasNext() {
return pEnum.hasMoreElements();
}
public T next() {
return pEnum.nextElement();
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
/**
* Adds all elements of the iterator to the collection.
*
* @param pCollection the collection
* @param pIterator the elements to add
*
* @throws UnsupportedOperationException if {@code add} is not supported by
* the given collection.
* @throws ClassCastException class of the specified element prevents it
* from being added to this collection.
* @throws NullPointerException if the specified element is null and this
* collection does not support null elements.
* @throws IllegalArgumentException some aspect of this element prevents
* it from being added to this collection.
*/
public static void addAll(Collection pCollection, Iterator pIterator) {
while (pIterator.hasNext()) {
pCollection.add(pIterator.next());
}
}
// Is there a usecase where Arrays.asList(pArray).iterator() can't ne used?
/**
* Creates a thin {@link Iterator} wrapper around an array.
*
* @param pArray the array to iterate
* @return a new {@link ListIterator}
* @throws IllegalArgumentException if {@code pArray} is {@code null},
* {@code pStart < 0}, or
* {@code pLength > pArray.length - pStart}
*/
public static ListIterator iterator(final E[] pArray) {
return iterator(pArray, 0, pArray.length);
}
/**
* Creates a thin {@link Iterator} wrapper around an array.
*
* @param pArray the array to iterate
* @param pStart the offset into the array
* @param pLength the number of elements to include in the iterator
* @return a new {@link ListIterator}
* @throws IllegalArgumentException if {@code pArray} is {@code null},
* {@code pStart < 0}, or
* {@code pLength > pArray.length - pStart}
*/
public static ListIterator iterator(final E[] pArray, final int pStart, final int pLength) {
return new ArrayIterator(pArray, pStart, pLength);
}
/**
* Creates an inverted mapping of the key/value pairs in the given map.
*
* @param pSource the source map
* @return a new {@code Map} of same type as {@code pSource}
* @throws IllegalArgumentException if {@code pSource == null},
* or if a new map can't be instantiated,
* or if source map contains duplaicates.
*
* @see #invert(java.util.Map, java.util.Map, DuplicateHandler)
*/
public static Map invert(Map pSource) {
return invert(pSource, null, null);
}
/**
* Creates an inverted mapping of the key/value pairs in the given map.
* Optionally, a duplicate handler may be specified, to resolve duplicate keys in the result map.
*
* @param pSource the source map
* @param pResult the map used to contain the result, may be {@code null},
* in that case a new {@code Map} of same type as {@code pSource} is created.
* The result map should be empty, otherwise duplicate values will need to be resolved.
* @param pHandler duplicate handler, may be {@code null} if source map don't contain dupliate values
* @return {@code pResult}, or a new {@code Map} if {@code pResult == null}
* @throws IllegalArgumentException if {@code pSource == null},
* or if result map is {@code null} and a new map can't be instantiated,
* or if source map contains duplicate values and {@code pHandler == null}.
*/
// TODO: Create a better duplicate handler, that takes Entries as parameters and returns an Entry
public static Map invert(Map pSource, Map pResult, DuplicateHandler pHandler) {
if (pSource == null) {
throw new IllegalArgumentException("source == null");
}
Map result = pResult;
if (result == null) {
try {
//noinspection unchecked
result = pSource.getClass().newInstance();
}
catch (InstantiationException e) {
// Handled below
}
catch (IllegalAccessException e) {
// Handled below
}
if (result == null) {
throw new IllegalArgumentException("result == null and source class " + pSource.getClass() + " cannot be instantiated.");
}
}
// Copy entries into result map, inversed
Set> entries = pSource.entrySet();
for (Map.Entry entry : entries) {
V newKey = entry.getValue();
K newValue = entry.getKey();
// Handle dupliates
if (result.containsKey(newKey)) {
if (pHandler != null) {
newValue = pHandler.resolve(result.get(newKey), newValue);
}
else {
throw new IllegalArgumentException("Result would include duplicate keys, but no DuplicateHandler specified.");
}
}
result.put(newKey, newValue);
}
return result;
}
public static Comparator reverseOrder(Comparator pOriginal) {
return new ReverseComparator(pOriginal);
}
private static class ReverseComparator implements Comparator {
private Comparator mComparator;
public ReverseComparator(Comparator pComparator) {
mComparator = pComparator;
}
public int compare(T pLeft, T pRight) {
int result = mComparator.compare(pLeft, pRight);
// We can't simply return -result, as -Integer.MIN_VALUE == Integer.MIN_VALUE.
return -(result | (result >>> 1));
}
}
@SuppressWarnings({"unchecked", "UnusedDeclaration"})
static , E> T generify(final Iterator pIterator, final Class pElementType) {
return (T) pIterator;
}
@SuppressWarnings({"unchecked", "UnusedDeclaration"})
static , E> T generify(final Collection pCollection, final Class pElementType) {
return (T) pCollection;
}
@SuppressWarnings({"unchecked", "UnusedDeclaration"})
static , K, V> T generify(final Map pMap, final Class pKeyType, final Class pValueType) {
return (T) pMap;
}
@SuppressWarnings({"unchecked"})
static , E> T generify2(Collection pCollection) {
return (T) pCollection;
}
@SuppressWarnings({"UnusedDeclaration"})
static void test() {
List list = Collections.singletonList("foo");
@SuppressWarnings({"unchecked"})
Set set = new HashSet(list);
List strs0 = CollectionUtil.generify(list, String.class);
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