_128_Java_互斥锁以及懒汉式单例模式线程安全问题的解决

//懒汉式单例模式的线程安全问题
//对于一般的方法而言，使用同步代码块，可以考虑使用this
//对于静态方法而言，使用当前类本身来充当。
public class _001_TestMutexLock {
	//InnerClass
	private static class Singleton{
		
		private Singleton() {
			
		}
		private static Singleton instance=null;
		
		public static Singleton getInstance() {
			if(instance==null) {
				synchronized (Singleton.class) {
					if(instance==null) {
						instance=new Singleton();
					}
				}
			}
			return instance;
		}
		
	}
	
	public static void main(String[] args) {
		_001_TestMutexLock.Singleton a = new _001_TestMutexLock.Singleton();
		_001_TestMutexLock.Singleton b = new _001_TestMutexLock.Singleton();
		Singleton instance = a.getInstance();
		Singleton instance2 = b.getInstance();
		System.out.println(instance==instance2);
	}
}