《张孝祥高新技术视频》里面关于ThreadLocal一节的示例源代码ThreadLocalTest.java，当设置的共享变量为MyThreadScopeData类时，为什么应用懒汉式单例结果可以实现数据共享，而改成饿汉式就出错了呢？PS，为了演示方便，把B类关了。
       懒汉式数据共享，两个线程的data各自共享：

1.         private MyThreadScopeData() {
   
2.         }
   
3. 
   
4.         public static MyThreadScopeData getThreadInstance() {
   
5.                 MyThreadScopeData instance = map.get();
   
6.                 if (instance == null) {
   
7.                         instance = new MyThreadScopeData();
   
8.                         map.set(instance);
   
9.                 }
   
10.                 return instance;
    
11.         }
    
12.         private static ThreadLocal<MyThreadScopeData> map = new ThreadLocal<MyThreadScopeData>();
    
13. //        结果如下
    
14.         /*        Thread-0 has put data :633291546
    
15.         Thread-1 has put data :-1541764721
    
16.         A from Thread-1 get data :-1541764721
    
17.         A from Thread-1 getMyData: name-1541764721,-1541764721
    
18.         A from Thread-0 get data :633291546
    
19.         A from Thread-0 getMyData: name633291546,633291546*/

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      改为饿汉式后，Thread-1在调用A类方法输出的data跟之前不一样了：

1.         private MyThreadScopeData() {
   
2.         }
   
3. 
   
4.         public static MyThreadScopeData m = new MyThreadScopeData();
   
5.         private static ThreadLocal<MyThreadScopeData> map = new ThreadLocal<MyThreadScopeData>();
   
6. 
   
7.         public static/* synchronized */MyThreadScopeData getThreadInstance() {
   
8.                 map.set(m);
   
9.                 return map.get();
   
10.         }
    
11. //        结果如下
    
12. /*        Thread-1 has put data :1964655262
    
13.         Thread-0 has put data :-49614189
    
14.         A from Thread-1 get data :1964655262
    
15.         A from Thread-1 getMyData: name-49614189,-49614189
    
16.         A from Thread-0 get data :-49614189
    
17.         A from Thread-0 getMyData: name-49614189,-49614189
    
18. */

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       《张孝祥高新技术视频》里面关于ThreadLocal一节的示例源代码ThreadLocalTest.java，当设置的共享变量为MyThreadScopeData类时，为什么应用懒汉式单例结果可以实现数据共享，而改成饿汉式就出错了呢？PS，为了演示方便，把B类关了。
       懒汉式数据共享，两个线程的data各自共享：

1.         private MyThreadScopeData() {
   
2.         }
   
3. 
   
4.         public static MyThreadScopeData getThreadInstance() {
   
5.                 MyThreadScopeData instance = map.get();
   
6.                 if (instance == null) {
   
7.                         instance = new MyThreadScopeData();
   
8.                         map.set(instance);
   
9.                 }
   
10.                 return instance;
    
11.         }
    
12.         private static ThreadLocal<MyThreadScopeData> map = new ThreadLocal<MyThreadScopeData>();
    
13. //        结果如下
    
14.         /*        Thread-0 has put data :633291546
    
15.         Thread-1 has put data :-1541764721
    
16.         A from Thread-1 get data :-1541764721
    
17.         A from Thread-1 getMyData: name-1541764721,-1541764721
    
18.         A from Thread-0 get data :633291546
    
19.         A from Thread-0 getMyData: name633291546,633291546*/

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      改为饿汉式后，Thread-1在调用A类方法输出的data跟之前不一样了：

1.         private MyThreadScopeData() {
   
2.         }
   
3. 
   
4.         public static MyThreadScopeData m = new MyThreadScopeData();
   
5.         private static ThreadLocal<MyThreadScopeData> map = new ThreadLocal<MyThreadScopeData>();
   
6. 
   
7.         public static/* synchronized */MyThreadScopeData getThreadInstance() {
   
8.                 map.set(m);
   
9.                 return map.get();
   
10.         }
    
11. //        结果如下
    
12. /*        Thread-1 has put data :1964655262
    
13.         Thread-0 has put data :-49614189
    
14.         A from Thread-1 get data :1964655262
    
15.         A from Thread-1 getMyData: name-49614189,-49614189
    
16.         A from Thread-0 get data :-49614189
    
17.         A from Thread-0 getMyData: name-49614189,-49614189
    
18. */

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