单例模式-枚举类实现

public class SingletonObject {

        private SingletonObject(){

        }

        /**
         * 枚举类型是线程安全的，并且只会装载一次
         */
        private enum Singleton{
            INSTANCE;

            private final SingletonObject instance;

            Singleton(){
                instance = new SingletonObject();
            }

            private SingletonObject getInstance(){
                return instance;
            }
        }

        public static SingletonObject getInstance(){

            return Singleton.INSTANCE.getInstance();
        }
    }