95 lines
2.9 KiB
Java
95 lines
2.9 KiB
Java
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// Copyright 2013 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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package org.chromium.base;
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import android.util.Pair;
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import androidx.annotation.NonNull;
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import java.lang.ref.WeakReference;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.Iterator;
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import java.util.List;
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/**
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* Functions used for easier initialization of Java collections. Inspired by
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* functionality in com.google.common.collect in Guava but cherry-picked to
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* bare-minimum functionality to avoid bloat. (http://crbug.com/272790 provides
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* further details)
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*/
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public final class CollectionUtil {
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private CollectionUtil() {}
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@SafeVarargs
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public static <E> HashSet<E> newHashSet(E... elements) {
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HashSet<E> set = new HashSet<E>(elements.length);
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Collections.addAll(set, elements);
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return set;
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}
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@SafeVarargs
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public static <K, V> HashMap<K, V> newHashMap(Pair<? extends K, ? extends V>... entries) {
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HashMap<K, V> map = new HashMap<>();
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for (Pair<? extends K, ? extends V> entry : entries) {
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map.put(entry.first, entry.second);
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}
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return map;
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}
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public static boolean[] booleanListToBooleanArray(@NonNull List<Boolean> list) {
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boolean[] array = new boolean[list.size()];
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for (int i = 0; i < list.size(); i++) {
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array[i] = list.get(i);
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}
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return array;
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}
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public static int[] integerCollectionToIntArray(@NonNull Collection<Integer> collection) {
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int[] array = new int[collection.size()];
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int index = 0;
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for (int num : collection) {
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array[index] = num;
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index++;
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}
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return array;
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}
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public static long[] longListToLongArray(@NonNull List<Long> list) {
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long[] array = new long[list.size()];
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for (int i = 0; i < list.size(); i++) {
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array[i] = list.get(i);
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}
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return array;
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}
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/**
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* Removes null entries from the given collection and then returns a list of strong references.
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*
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* Note: This helper is relevant if you have a List<WeakReference<T>> or a Map with weak values.
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* For Set<WeakReference<T>>, use Collections.newSetFromMap(new WeakHashMap()) instead.
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*
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* @param weakRefs Collection to iterate.
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* @return List of strong references.
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*/
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public static <T> List<T> strengthen(Collection<WeakReference<T>> weakRefs) {
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ArrayList<T> ret = new ArrayList<>(weakRefs.size());
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Iterator<WeakReference<T>> it = weakRefs.iterator();
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while (it.hasNext()) {
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WeakReference<T> weakRef = it.next();
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T strongRef = weakRef.get();
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if (strongRef == null) {
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it.remove();
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} else {
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ret.add(strongRef);
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}
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}
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return ret;
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}
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}
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