ThreadLocal和InheritableThreadLocal區別，可以用程式碼測試一下：

1. package com.lang;  
2. import junit.framework.TestCase;  
3. import static java.lang.System.out;  
4. public class TestInheritableThreadLocal extends TestCase {  
5.     public void testThreadLocal() {  
6.         final ThreadLocal<String> local = new
    ThreadLocal<String>();  
7.         work(local);  
8.     }  
9.     public void testInheritableThreadLocal() {  
10.         final ThreadLocal<String> local = new InheritableThreadLocal<String>();  
11.         work(local);  
12.     }  
13.     private void work(final ThreadLocal<String> local) {  
14.         local.set("a");  
15.         out.println(Thread.currentThread() + "," + local.get());  
16.         Thread t = new Thread(new Runnable() {  
17.             @Override  
18.             public void run() {  
19.                 out.println(Thread.currentThread() + "," + local.get());  
20.                 local.set("b"
    );  
21.                 out.println(Thread.currentThread() + "," + local.get());  
22.             }  
23.         });  
24.         t.start();  
25.         try {  
26.             t.join();  
27.         } catch (InterruptedException e) {  
28.             e.printStackTrace();  
29.         }  
30.         out.println(Thread.currentThread() + "," + local.get());  
31.     }  
32. }  

執行testThreadLocal，輸出：

1. Thread[main,5,main],a  
2. Thread[Thread-0,5,main],null  
3. Thread[Thread-0,5,main],b  
4. Thread[main,5,main],a  

執行testInheritableThreadLocal，輸出：

1. Thread[main,5,main],a  
2. Thread[Thread-0,5,main],a  
3. Thread[Thread-0,5,main],b  
4. Thread[main,5,main],a  

比較後，看到ThreadLocal裡的值，子執行緒裡不能獲得；InheritableThreadLocal裡的值，子執行緒可以獲得。