ThreadLocal的使用

看http://docs.oracle.com/javase/6/docs/api/java/lang/ThreadLocal.html了解了一些基本使用，但是发现里面的代码有问题

检查了一下，原来是getCurrentThreadId()应该return uniqueNum.get()而不是return uniqueId.get()

改写如下：

// Each thread has its own 'thread-ID' even if 'uniqueNum' is static

class UniqueThreadIdGenerator {

    private static final AtomicInteger uniqueId = new AtomicInteger(0);



    private static final ThreadLocal<Integer> uniqueNum = 

        new ThreadLocal<Integer>() {

            @Override

            protected Integer initialValue() {

                return uniqueId.getAndIncrement();

            }

        };



    public static int getCurrentThreadId() {

        return uniqueNum.get();

    }

}



class Runner implements Runnable {

    @Override

    public void run() {

        try {

            while (!Thread.interrupted()) {

                System.out.println(UniqueThreadIdGenerator.getCurrentThreadId());

                TimeUnit.MILLISECONDS.sleep(500);

            }

        } catch (Exception e) {

        }

    }

}



public class Foo { 

    public static void main(String[] args) throws IOException { 

        ExecutorService exec = Executors.newCachedThreadPool();

        exec.execute(new Runner());

        exec.execute(new Runner());

        System.in.read();

        exec.shutdownNow();

    }

}