microsoft.exchange.webservices.data.core.LazyMember Maven / Gradle / Ivy
/*
* The MIT License
* Copyright (c) 2012 Microsoft Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package microsoft.exchange.webservices.data.core;
/**
* Wrapper class for lazy members. Does lazy initialization of member on first
* access.
*
* @param Type of the lazy member
*
* If we find ourselves creating a whole bunch of these in our code,
* we need to rethink this. Each lazy member holds the actual member
* and a delegate. That can turn into a whole lot of overhead
*
*/
public class LazyMember {
/**
* The lazy member.
*/
private volatile T lazyMember;
/**
* The lazy implementation.
*/
private final ILazyMember lazyImplementation;
/**
* Public accessor for the lazy member. Lazy initializes the member on first
* access
*
* @return the member
*/
public T getMember() {
T result = this.lazyMember;
if (result == null) { // first check (no locking)
synchronized (this) {
result = this.lazyMember;
if (result == null) { // second check (with locking)
this.lazyMember = result = lazyImplementation.createInstance();
}
}
}
return result;
}
/**
* Constructor.
*
* @param lazyImplementation The initialization delegate to call for the item on first
* access
*/
public LazyMember(ILazyMember lazyImplementation) {
this.lazyImplementation = lazyImplementation;
}
}