Java中的五種單例模式實現方法

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[代碼] Java中的五種單例模式實現方法  

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package singleton; /** * @author lei * 單例模式的五種寫法： * 1、懶漢 * 2、惡漢 * 3、靜態內部類 * 4、枚舉 * 5、雙重校正鎖 * 2011-9-6 *//** *五、 雙重校正鎖，在當前的記憶體模型中無效 */class LockSingleton{    private volatile static LockSingleton singleton;    private LockSingleton(){}         //詳見：http://www.ibm.com/developerworks/cn/java/j-dcl.html    public static LockSingleton getInstance(){        if(singleton==null){            synchronized(LockSingleton.class){                if(singleton==null){                    singleton=new LockSingleton();                }            }        }        return singleton;    }     }/** * 四、枚舉，《Effective Java》作者推薦使用的方法，優點：不僅能避免多線程同步問題，而且還能防止還原序列化重新建立新的對象 */enum EnumSingleton{    INSTANCE;    public void doSomeThing(){    }}/** * 三、靜態內部類 優點：載入時不會初始化靜態變數INSTANCE，因為沒有主動使用，達到Lazy loading */class InternalSingleton{    private static class SingletonHolder{        private final static  InternalSingleton INSTANCE=new InternalSingleton();    }       private InternalSingleton(){}    public static InternalSingleton getInstance(){        return SingletonHolder.INSTANCE;    }}/** * 二、惡漢,缺點：沒有達到lazy loading的效果 */class HungrySingleton{    private static HungrySingleton singleton=new HungrySingleton();    private HungrySingleton(){}    public static HungrySingleton getInstance(){        return singleton;    }}/** * 一、懶漢，常用的寫法 */class LazySingleton{    private static LazySingleton singleton;    private LazySingleton(){    }    public static LazySingleton getInstance(){        if(singleton==null){            singleton=new LazySingleton();        }        return singleton;    }   }

Java中的五種單例模式實現方法