單例設計模式懶漢式和惡漢式

一,單例設計模式懶漢式和惡漢式

懶漢式在類加載時不初始化，延遲加載。（配置文件）

餓漢式在類加載時初始化，加載慢，獲取對象快。

餓漢式是線程安全的，

懶漢式需要加synchronized，否則不安全。

二，餓漢式

public class Singletonehan {
    private static  Singletonehan singleton=new Singletonehan();
    private Singletonehan() {
    }
public static Singletonehan getInstance(){
        return singleton;
}

    @Override
    public String toString() {
        return "Singletonehan{}";
    }
}

測試

public class testehan {
    public static void main(String[] args) {
        Singletonehan singletonehan = Singletonehan.getInstance();
        System.out.println(singletonehan);
    }
}

三，懶漢式

public class Singletonlanhan {
   // private static  Singletonlanhan singleton=new Singletonlanhan();
    private static  Singletonlanhan singleton=null;

    private Singletonlanhan() {
    }

    public static Singletonlanhan getInstance() {
        if (singleton == null) {
            singleton = new Singletonlanhan();
        }
        return singleton;
    }

    @Override
    public String toString() {
        return "Singletonlanhan{}";
    }
}

測試

public class test {
    public static void main(String[] args) {
        Singletonlanhan singletonlanhan = Singletonlanhan.getInstance();
        System.out.println(singletonlanhan);
    }
}

結果

Singletonlanhan{}

Process finished with exit code 0

補充加synchronized后的懶漢

public class Singletonlanhan {
   // private static  Singletonlanhan singleton=new Singletonlanhan();
    private static  Singletonlanhan singleton=null;

    private Singletonlanhan() {
    }

    public synchronized static Singletonlanhan getInstance() {
        if (singleton == null) {
            singleton = new Singletonlanhan();
        }
        return singleton;
    }

    @Override
    public String toString() {
        return "鎖Singletonlanhan{}";
    }
}

結果

鎖Singletonlanhan{}

Process finished with exit code 0