/*
* Copyright 2012 the original author or authors.
*
* 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 org.gradle.internal;
import java.lang.ref.SoftReference;
import java.util.concurrent.atomic.AtomicReference;
public abstract class Factories {
public static <T> Factory<T> toFactory(final Runnable runnable) {
return new Factory<T>() {
public T create() {
runnable.run();
return null;
}
};
}
public static <T> Factory<T> constant(final T item) {
return new Factory<T>() {
public T create() {
return item;
}
};
}
public static <T> Factory<T> constantNull() {
return constant(null);
}
public static <T> Factory<T> softReferenceCache(Factory<T> factory) {
return new CachingSoftReferenceFactory<T>(factory);
}
private static class CachingSoftReferenceFactory<T> implements Factory<T> {
private final Factory<T> factory;
private final AtomicReference<SoftReference<T>> cachedReference = new AtomicReference<SoftReference<T>>();
public CachingSoftReferenceFactory(Factory<T> factory) {
this.factory = factory;
}
public T create() {
SoftReference<T> reference = cachedReference.get();
T value = reference != null ? reference.get() : null;
if (value == null) {
value = factory.create();
cachedReference.set(new SoftReference<T>(value));
}
return value;
}
}
}