net.hasor.utils.supplier.SingleProvider Maven / Gradle / Ivy
/*
* Copyright 2008-2009 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 net.hasor.utils.supplier;
import java.util.function.Supplier;
/**
* 单例对象的{@link Supplier}封装形式。
* @version : 2014年7月8日
* @author 赵永春 ([email protected])
*/
public class SingleProvider implements Supplier {
private Supplier provider = null;
private volatile T instance = null;
private final Object lock = new Object();
public SingleProvider(Supplier provider) {
this.provider = provider;
}
public T get() {
if (this.instance == null) {
synchronized (this.lock) {
if (this.instance == null) {
this.instance = newInstance(this.provider);
}
}
}
return this.instance;
}
protected T newInstance(Supplier provider) {
return provider.get();
}
public String toString() {
return "SingleProvider->" + provider.toString();
}
}