单例设计模式懒汉式和恶汉式

Posted 2022-02-24 fengtangjiang

一,单例设计模式懒汉式和恶汉式

懒汉式在类加载时不初始化，延迟加载。（配置文件）

饿汉式在类加载时初始化，加载慢，获取对象快。

饿汉式是线程安全的，

懒汉式需要加synchronized，否则不安全。

二，饿汉式

 1 public class Singletonehan 
 2     private static  Singletonehan singleton=new Singletonehan();
 3     private Singletonehan() 
 4     
 5 public static Singletonehan getInstance()
 6         return singleton;
 7 
 8 
 9     @Override
10     public String toString() 
11         return "Singletonehan";
12     
13 

测试

1 public class testehan 
2     public static void main(String[] args) 
3         Singletonehan singletonehan = Singletonehan.getInstance();
4         System.out.println(singletonehan);
5     
6 

三，懒汉式

 1 public class Singletonlanhan 
 2    // private static  Singletonlanhan singleton=new Singletonlanhan();
 3     private static  Singletonlanhan singleton=null;
 4 
 5     private Singletonlanhan() 
 6     
 7 
 8     public static Singletonlanhan getInstance() 
 9         if (singleton == null) 
10             singleton = new Singletonlanhan();
11         
12         return singleton;
13     
14 
15     @Override
16     public String toString() 
17         return "Singletonlanhan";
18     
19 

测试

1 public class test 
2     public static void main(String[] args) 
3         Singletonlanhan singletonlanhan = Singletonlanhan.getInstance();
4         System.out.println(singletonlanhan);
5     
6 

结果

Singletonlanhan

Process finished with exit code 0

补充加synchronized后的懒汉

 1 public class Singletonlanhan 
 2    // private static  Singletonlanhan singleton=new Singletonlanhan();
 3     private static  Singletonlanhan singleton=null;
 4 
 5     private Singletonlanhan() 
 6     
 7 
 8     public synchronized static Singletonlanhan getInstance() 
 9         if (singleton == null) 
10             singleton = new Singletonlanhan();
11         
12         return singleton;
13     
14 
15     @Override
16     public String toString() 
17         return "锁Singletonlanhan";
18     
19 

结果

锁Singletonlanhan

Process finished with exit code 0