实现单例模式的几种方式

时间 2019-11-19

标签实现模式几种方式繁體版

原文原文链接

1：饿汉模式java

public class MyObject {
  // 当即加载方式 == 饿汉模式
  private static MyObject myObject= new MyObject();
  private MyObject(){}
  public static MyObject getInstance(){
    return myObject;
  }
}

2：懒汉模式code

public class MyObject {
  private static MyObject myObject;
  private MyObject(){}
  synchronized public static MyObject getInstance(){
    if (myObject == null) {
      myObject = new MyObject();
    }
    return myObject;
  }
}

注意：加入同步synchronized关键字获得相同实例的对象，但此种方式的运行效率很是低。对象

解决方法：使用DCL（Double-Check Locking）get

public class MyObject {
  private static MyObject myObject;
  private MyObject(){}
  public static MyObject getInstance(){
    if (myObject == null) {
      synchronized (MyObject.class) {
        if (myObject == null) {
          myObject = new MyObject();
        }
      }
    }
    return myObject;
  }
}

3：静态内置类同步

public class MyObject {
    private static class MyObjectHandler{
        private static MyObject myObject = new MyObject();
    }
    private MyObject() {
    }
    synchronized public static MyObject getInstance() {
        
        return MyObjectHandler.myObject;
    }
}

4：序列化与反序列化的单例模式实现io

public class MyObjectSerializable implements Serializable {
    private static final long serialVersionUID = 888L;
     private static class MyObjectHandler{
         private static final MyObjectSerializable myObject = new MyObjectSerializable();
     }
     private MyObjectSerializable() {

     }
     protected Object readResolve() throws ObjectStreamException {
         return MyObjectHandler.myObject;
     }

}

5：使用静态代码块class

public class MyObject {
    private static MyObject myObject;
    static {
        myObject = new MyObject();
    }
    private MyObject() {
    }
    synchronized public static MyObject getInstance() {

        return myObject;
    }
}

6：使用enum枚举数据类型效率