core/java/com/google/android/collect/Lists.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.android.collect;

import java.util.ArrayList;
import java.util.Collections;

/**
 * Provides static methods for creating {@code List} instances easily, and other
 * utility methods for working with lists. 
 */
public class Lists {

    /**
     * Creates an empty {@code ArrayList} instance.
     *
     * <p><b>Note:</b> if you only need an <i>immutable</i> empty List, use
     * {@link Collections#emptyList} instead.
     *
     * @return a newly-created, initially-empty {@code ArrayList}
     */
    public static <E> ArrayList<E> newArrayList() {
        return new ArrayList<E>();
    }

    /**
     * Creates a resizable {@code ArrayList} instance containing the given
     * elements.
     *
     * <p><b>Note:</b> due to a bug in javac 1.5.0_06, we cannot support the
     * following:
     *
     * <p>{@code List<Base> list = Lists.newArrayList(sub1, sub2);}
     *
     * <p>where {@code sub1} and {@code sub2} are references to subtypes of
     * {@code Base}, not of {@code Base} itself. To get around this, you must
     * use:
     *
     * <p>{@code List<Base> list = Lists.<Base>newArrayList(sub1, sub2);}
     *
     * @param elements the elements that the list should contain, in order
     * @return a newly-created {@code ArrayList} containing those elements
     */
    public static <E> ArrayList<E> newArrayList(E... elements) {
        int capacity = (elements.length * 110) / 100 + 5;
        ArrayList<E> list = new ArrayList<E>(capacity);
        Collections.addAll(list, elements);
        return list;
    }
}