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The source code is released under:

Apache License

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/*******************************************************************************
 * Copyright 2011 See AUTHORS file.//www.  j av a2 s . c  o m
 * 
 * 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.badlogic.gdx.utils;

/**
 * A pool of objects that can be reused to avoid allocation.
 * 
 * @author Nathan Sweet
 */
abstract public class Pool<T> {
    public final int max;

    private final Array<T> freeObjects;

    /** Creates a pool with an initial capacity of 16 and no maximum. */
    public Pool() {
        this(16, Integer.MAX_VALUE);
    }

    /** Creates a pool with the specified initial capacity and no maximum. */
    public Pool(int initialCapacity) {
        this(initialCapacity, Integer.MAX_VALUE);
    }

    /**
     * @param max
     *            The maximum number of free objects to store in this pool.
     */
    public Pool(int initialCapacity, int max) {
        freeObjects = new Array(false, initialCapacity);
        this.max = max;
    }

    abstract protected T newObject();

    /**
     * Returns an object from this pool. The object may be new (from
     * {@link #newObject()}) or reused (previously {@link #free(Object) freed}).
     */
    public T obtain() {
        return freeObjects.size == 0 ? newObject() : freeObjects.pop();
    }

    /**
     * Puts the specified object in the pool, making it eligible to be returned
     * by {@link #obtain()}. If the pool already contains {@link #max} free
     * objects, the specified object is ignored.
     */
    public void free(T object) {
        if (object == null)
            throw new IllegalArgumentException("object cannot be null.");
        if (freeObjects.size < max)
            freeObjects.add(object);
        if (object instanceof Poolable)
            ((Poolable) object).reset();
    }

    /**
     * Puts the specified objects in the pool.
     * 
     * @see #free(Object)
     */
    public void free(Array<T> objects) {
        for (int i = 0, n = Math.min(objects.size, max - freeObjects.size); i < n; i++) {
            T object = objects.get(i);
            freeObjects.add(object);
            if (object instanceof Poolable)
                ((Poolable) object).reset();
        }
    }

    /** Removes all free objects from this pool. */
    public void clear() {
        freeObjects.clear();
    }

    /**
     * Objects implementing this interface will have {@link #reset()} called
     * when passed to {@link #free(Object)}.
     */
    static public interface Poolable {
        /**
         * Resets the object for reuse. Object references should be nulled and
         * fields may be set to default values.
         */
        public void reset();
    }
}

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