单例模式

饿汉式 public class Singleton { private final static Singleton instance = new Singleton(); private Singleton(){} public static Singleton getInstance(){ return instance; } }

懒汉式

public class Singleton { private final static Singleton instance; private Singleton(){} public static Singleton getInstance(){ if(instance==null){ instance = new Singleton(); } return instance; } }

多线程下的单例

public class Singleton { private final static Singleton instance; private final static Object syn = new Object(); private Singleton(){} public static Singleton getInstance(){ if(instance==null){ lock(syn){ if(instance==null){ instance = new Singleton(); } } } return instance; } }