关于多线程的一个程序

Question

public class Joining{
static Thread createThread(final int i, final Thread t1) {
Thread t2 = new Thread(){
public void run(){
System.out.println(i+1);
try{
t1.join();
}catch (InterruptedException e) {
}
System.out.println(i+2);
}
};
System.out.println(i+3);
t2.start();
System.out.println(i+4);
return t2;
}
public static void main(String[] args) {
createThread(10,createThread(20,Thread.currentThread()));
}
}
这个程序难吗，有多少人能看出答案来，看出来的讲解一下列！

Answer 1

public class Test {    static Thread createThread(final int i, final Thread t1) {
        Thread t2 = new Thread() {            public void run() {
                System.out.println(Thread.currentThread().getName() + ":" + (i + 1));
                try {
                    t1.join();
                } catch (InterruptedException e) {
                }
                System.out.println(Thread.currentThread().getName() + ":" + (i + 2));
            }
        };
        System.out.println(Thread.currentThread().getName() + ":" + (i + 3));
        t2.start();
        System.out.println(Thread.currentThread().getName() + ":" + (i + 4));
        return t2;
    }    public static void main(String[] args) {
        createThread(10, createThread(20, Thread.currentThread()));
    }
} 这样改一下,再单步调试一下,可以观察每一步中每个线程的状态,应该很容易明白了.