1. 懶漢模式，雙層檢查機制

public class SingleOne {


    private static volatile Object object=null;


    /**
     * 懶漢模式
     * 雙重判斷模式
     * @return
     */
    public static Object getInstance(){
        if(object==null){
            synchronized (SingleOne.class){
                if(object==null){
                    object
 
=new Object();
                }
            }
        }
        return object;
    }
}

2. 餓漢模式（內部類靜態類）

public class SingleTwo {


    /**
     * 餓漢模式
     * 靜態內部類方式
     */
    private static class ObjectHandler{
        private static Object object = new Object();
    }

    private SingleTwo(){

    }

    
 
public static SingleTwo getInstance(){
      return   ObjectHandler.object;
    }


}

3. 餓漢模式（靜態程式碼塊）

    private static Object instance = null;

    private SingleThree(){}

    /**
     * 靜態內部類方式
     */
    static {
        instance = new Object();
    }

    public static SingleThree getInstance(){
        
 
return instance;
    }