对包含静态成员的现有类使用ThreadLocal

我正在尝试使用 ThreadLocal 为预先存在的非线程安全类提供线程安全,但遇到了问题。似乎没有执行隔离——线程仍然共享静态,而不是每个线程的本地。

我相信我的用法几乎与示例本地化完全平行 SimpleDateFormatter 描述于 this StackOverflow question 但事情并没有像我希望的那样发展。

我希望有人能指出我一定犯了一个极其愚蠢的错误。..所以我想我的问题是:你能发现我在这里做错了什么吗?

public class SimpleClassWithStaticMembers {
    private static String theStaticString =
        "StaticStringInClassWithStaticMember";
    public void setTheStaticString (String val) {
        SimpleClassWithStaticMembers.theStaticString = val; 
    }
    public String getTheStaticString () {
        return SimpleClassWithStaticMembers.theStaticString;
    }
}

这是创建以下线程局部实例的线程类 SimpleClassWithStaticMembers :

public class SimpleTesterThread extends Thread {
    private void showMsg (String msg) {  
        System.out.println (msg); 
        System.out.flush(); 
    }
    public SimpleTesterThread (String threadId) {
        super(threadId);
    }
    public void run() {
        try { Thread.sleep(2000); } catch (InterruptedException ex) { }
        ThreadLocal<SimpleClassWithStaticMembers> localizedClass =
            new ThreadLocal<SimpleClassWithStaticMembers>();
        localizedClass.set(new SimpleClassWithStaticMembers());
        // repeating here to be sure we overlap all with all
        for (int ii=0; ii < 3; ii++) { 
            localizedClass.get().setTheStaticString ("Setby_" + this.getName());
            try { Thread.sleep(2000); } catch (InterruptedException ex) { }
            showMsg("            Thread [" + this.getName() + "] - " 
                + localizedClass.get().getTheStaticString() + "'.");
        }
        showMsg ("Thread [" + this.getName() 
            + "] complete. Our 'threadlocal' string is now - " 
            + localizedClass.get().getTheStaticString() + "'.");
        localizedClass.remove();
    }
}

当十个实例 SimpleTesterThread 创建(给它们不同的线程名称,如“AAAAAAAAAA”、“BBBBBBBBB”等),然后启动,输出清楚地表明它们正在共享实例。日志输出包括:

...
            Thread [JJJJJJJJJJ] - Setby_CCCCCCCCCC'.
            Thread [DDDDDDDDDD] - Setby_JJJJJJJJJJ'.
            Thread [IIIIIIIIII] - Setby_DDDDDDDDDD'.
            Thread [GGGGGGGGGG] - Setby_IIIIIIIIII'.
            Thread [EEEEEEEEEE] - Setby_GGGGGGGGGG'.
Thread [EEEEEEEEEE] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
            Thread [HHHHHHHHHH] - Setby_GGGGGGGGGG'.
            Thread [BBBBBBBBBB] - Setby_GGGGGGGGGG'.
            Thread [FFFFFFFFFF] - Setby_GGGGGGGGGG'.
Thread [FFFFFFFFFF] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
...
            Thread [JJJJJJJJJJ] - Setby_GGGGGGGGGG'.
Thread [JJJJJJJJJJ] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
Thread [HHHHHHHHHH] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
            Thread [GGGGGGGGGG] - Setby_GGGGGGGGGG'.
Thread [GGGGGGGGGG] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
            Thread [IIIIIIIIII] - Setby_GGGGGGGGGG'.
            Thread [CCCCCCCCCC] - Setby_GGGGGGGGGG'.
Thread [CCCCCCCCCC] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
Thread [AAAAAAAAAA] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
            Thread [DDDDDDDDDD] - Setby_GGGGGGGGGG'.
Thread [DDDDDDDDDD] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
Thread [IIIIIIIIII] complete. Our 'threadlocal' string is now - Setby_GGGGGGGGGG'.
============== all threads complete.

我还没有包括创建、启动和连接线程的类——如果觉得有帮助,我很乐意编辑添加它。