Java 雙層校驗鎖單列模式

//雙層校驗鎖單列模式

public class Singleton{

private static Singleton singleton ;

private Singleton() {}

public static Singleton getInstance() {

if(singleton==null) {

synchronized (singleton) {

if(singleton == null) {

singleton=new Singleton();

}

}

}

return singleton;

}

}