有人可以解释为什么程序没有结束吗？

Question

Hi, I'm new to the java thread.I'm trying to figure out what is the wait() and notify() methods.So I wrote simple programme but I can't find the reason for infinity execution.Please, can someone help me to solve this?

public class StairCase {
    public static void main(String[] args) {
        int[] lst = {1,2,3,4,5,6,7};
        Test1 t1 = new Test1(lst);
        t1.setName("Test 1 ");
        Test2 t2 = new Test2(lst);
        t2.setName("Test 2 ");
        t1.start();
        t2.start();
    }
}

class Test1 extends Thread {
    int[] line ;
    public Test1(int[] lst) {
        this.line = lst;
    }
    public void run(){
        synchronized(line) {
            for (int i = 0; i < 5; i++) {
                try{
                    if(i == 2) line.wait();
               } catch (Exception e) {

               }
               System.out.println(Thread.currentThread().getName() + line[i]);
            }
        }
    }

}

class Test2 extends Thread {
    int[] line ;
    public Test2(int[] lst) {
        this.line = lst;
    }
    public void run() {
        synchronized(line) {
            for (int i = 0; i < 5; i++) {
                System.out.println(Thread.currentThread().getName() + line[i]);
            }
        }
        try {
            line.notify();
        } catch(Exception e) {
        }
    }
}

Answer 1

public class StairCase {
    public static void main(String[] args) {
        int[] lst = {1,2,3,4,5,6,7};
        Test1 t1 = new Test1(lst);
        t1.setName("Test 1 ");
        Test2 t2 = new Test2(lst);
        t2.setName("Test 2 ");
        t1.start();
        t2.start();
    }
}

class Test1 extends Thread {
    private final int[] line ;
    Test1(int[] lst) {
        this.line = lst;
    }
    public void run(){
        synchronized(line) {
            for (int i = 0; i < 5; i++) {
                try{
                    if(i == 2) line.wait();
                } catch (Exception e) {
                  e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + line[i]);
            }
        }
    }

}

class Test2 extends Thread {
    private final int[] line ;
    Test2(int[] lst) {
        this.line = lst;
    }
    public void run() {
        synchronized(line) {
            for (int i = 0; i < 5; i++) {
                System.out.println(Thread.currentThread().getName() + line[i]);
            }
        }
        try {
            synchronized (line) {
                line.notify();
            }
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
}

试试这个代码这是你期望的结果吗？如果没有，请告诉我预期结果是什么。

我添加了e.printStackTrace()；到 catch 块并检查天气是否有异常，并且有一个异常，异常在 notify() 的第 45 行所以我用同步语句包围了通知。

        synchronized (line) {
            line.notify();
        }

有人可以解释为什么程序没有结束吗？

Can some one explain why program doesn't end?

java

concurrency

multithreading

notify

wait