典型的线程安全

public class A1 {
	public static ThreadLocal tl = new ThreadLocal(); 
	static Integer a=1;
	public static void main(String[] args) {
		for (int i = 0; i < 3; i++) {
			new Thread() {
				public void run() {
					try {
						synchronized (a) {
							Thread.sleep(10);
							tl.set(Thread.currentThread().getName()+"-----"+a++);
							System.out.println(Thread.currentThread().getName()+"-----"+tl.get());
//						b.getTl().remove();
						}
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
			}.start();
		}
	}
}