Java 同步单例设计模式

//饿汉式class Single{private static final Single s=new Single();private Single(){}public static Single getInstance(){return s;}}//懒汉式class Single{private static s=null;private Single(){}public static Single getInstance(){if(s==null){//防止加同步降低效率 必须等于Null再判断同步synchronized(Single.class){//防止多线程出现问题if(s==null)//->0 ->1 线程到这里被切换 会new 多个对象 所以要加同步s=new Single();return s; }}}}