一个理解“单例模式”最好的例子
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public class SingletonTest { public static void main(String[] args){ Singleton s1=Singleton.getInstance(); Singleton s2=Singleton.getInstance(); System.out.println("s1=s2?"+(s1==s2)); System.out.println("s1.getNextID="+s1.getNextID()); System.out.println("s2.getNextID="+s2.getNextID()); System.out.println("s1.getNextID="+s1.getNextID()); } } class Singleton{ private static int nextID=0; private static Singleton instance=null; private Singleton(){}; public static synchronized Singleton getInstance(){ if(instance==null){ instance=new Singleton(); } return instance; }