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/**
* Copyright (c) 2012, Google Inc.
*
* 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.android.mail.utils;
import com.google.common.collect.Lists;
import java.util.Deque;
/**
* This class maintains a cache of soft references to objects. This allows callers to use a pool
* of object instances
* @param <T>
*/
public class ObjectCache<T> {
public interface Callback<T> {
T newInstance();
void onObjectReleased(T object);
}
private final Deque<T> mDataStore = Lists.newLinkedList();
private final Callback<T> mCallback;
private final int mMaxSize;
/**
* Creates a new ObjectCache instance
* @param callbacks Callback object that that will return a new instance of the object, and
* perform any cleanup when the object is released back to the cache
*/
public ObjectCache(Callback<T> callbacks, int maxSize) {
mCallback = callbacks;
mMaxSize = maxSize;
}
/**
* Returns an instance of the specified object type, creating a new instance if needed.
*/
public T get() {
T result;
synchronized (mDataStore) {
result = mDataStore.poll();
}
if (result == null) {
result = mCallback.newInstance();
}
return result;
}
/**
* Releases the specified object back to the cache. Once an object is released, it can be
* returned by subsequent calls to get()
*/
public void release(T objectToCache) {
synchronized (mDataStore) {
if (mDataStore.size() < mMaxSize) {
mCallback.onObjectReleased(objectToCache);
mDataStore.add(objectToCache);
}
}
}
}
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