Question

代码1：

// Create a second thread.
class NewThread implements Runnable {
    Thread t;
    NewThread() {
        // Create a new, second thread
        t = new Thread(this, "Demo Thread");
        System.out.println("Child thread: " + t);
        t.start(); // Start the thread
    }
    // This is the entry point for the second thread.
    public void run() {
        try {
            for(int i = 5; i > 0; i--) {
                System.out.println("Child Thread: " + i);
                Thread.sleep(500);
            }
        } catch (InterruptedException e) {
            System.out.println("Child interrupted.");
        }
        System.out.println("Exiting child thread.");
    }
}

class ThreadDemo {
    public static void main(String args[ ] ) {
        new NewThread(); // create a new thread
        try {
            for(int i = 5; i > 0; i--) {
                System.out.println("Main Thread: " + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            System.out.println("Main thread interrupted.");
        }
        System.out.println("Main thread exiting.");
    }
}

代码1（输出）：

Child thread: Thread[Demo Thread,5,main]
Main Thread: 5
Child Thread: 5
Child Thread: 4
Main Thread: 4
Child Thread: 3
Child Thread: 2
Main Thread: 3
Child Thread: 1
Exiting child thread.
Main Thread: 2
Main Thread: 1
Main thread exiting.

代码2：

// Using join() to wait for threads to finish.
class NewThread implements Runnable {
    String name; // name of thread
    Thread t;
    NewThread(String threadname) {
        name = threadname;
        t = new Thread(this, name);
        System.out.println("New thread: " + t);
        t.start(); // Start the thread
    }
    // This is the entry point for thread.
    public void run() {
        try {
            for(int i = 5; i > 0; i--) {
                System.out.println(name + ": " + i);
                Thread.sleep(1000);
            }
        } catch (InterruptedException e) {
            System.out.println(name + " interrupted.");
        }
        System.out.println(name + " exiting.");
    }
}

class DemoJoin {
    public static void main(String args[]) {
        NewThread ob1 = new NewThread("One");
        NewThread ob2 = new NewThread("Two");
        NewThread ob3 = new NewThread("Three");
        System.out.println("Thread One is alive: "
            + ob1.t.isAlive());
        System.out.println("Thread Two is alive: "
            + ob2.t.isAlive());
        System.out.println("Thread Three is alive: "
            + ob3.t.isAlive());
        // wait for threads to finish
        try {
            System.out.println("Waiting for threads to finish.");
            ob1.t.join();
            ob2.t.join();
            ob3.t.join();
        } catch (InterruptedException e) {
            System.out.println("Main thread Interrupted");
        }
        System.out.println("Thread One is alive: "
            + ob1.t.isAlive());
        System.out.println("Thread Two is alive: "
            + ob2.t.isAlive());
        System.out.println("Thread Three is alive: "
            + ob3.t.isAlive());
        System.out.println("Main thread exiting.");
    }
}

Code2（输出） - 每次运行时都会改变：

New thread: Thread[One,5,main]
New thread: Thread[Two,5,main]
New thread: Thread[Three,5,main]
Thread One is alive: true
Two: 5
One: 5
Thread Two is alive: true
Thread Three is alive: true
Waiting for threads to finish.
Three: 5
Two: 4
One: 4
Three: 4
Two: 3
One: 3
Three: 3
Three: 2
One: 2
Two: 2
One: 1
Three: 1
Two: 1
Two exiting.
One exiting.
Three exiting.
Thread One is alive: false
Thread Two is alive: false
Thread Three is alive: false
Main thread exiting.

嗨，那里。我希望你看看这些代码。问题是：start（）方法的行为有何不同？据我所知，主线程应该是运行的，直到方法sleep（），join（）等等。＆＃34;发生＆＃34;，当发生这种情况时，Scheduler应该获得Ready队列的下一个线程并将她设置为Thread ::运行。是因为join（）方法还是什么？我有线程的基本知识，但这段代码非常困扰我。提前谢谢。

join（）和start（）方法

0 个答案: