从3个线程按顺序打印3个不同的数字范围

Question

采访中问

有三条线。第一条线打印100到199个数字。第二个线程打印200到299之间的数字。第三条线从300到399。执行的顺序是

Thread100to199:100
Thread200to299:200
Thread300to399:300
Thread100to199:101
Thread200to299:201
Thread300to399:301
::::::::::::::::::
Thread300to399:398
Thread100to199:199
Thread200to299:299
Thread300to399:399

Answer 1

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * This class prints Range of numbers from 100-199, 200-299 and 300-399 from the
 * Thread100to199, Thread200to299 and Thread300to399 respectively.
 * The order of printing the Numbers/ order of running the threads is as follows
 * Thread100to199:100
 * Thread200to299:200
 * Thread300to399:300
 * Thread100to199:101
 * Thread200to299:201
 * Thread300to399:301
 * ::::::::::::::::::
 * Thread300to399:398
 * Thread100to199:199
 * Thread200to299:299
 * Thread300to399:399
 *
 */
public class RangeOrderedThread {

    static Lock lock = new ReentrantLock();
    static Condition cond = lock.newCondition();
    static int nextThreadRunCode ;

    public static void main(String[] args) {

        Thread t1 = new ThreadPrintRange(100,199);
        t1.setName("Thread100to199");
        Thread t2 = new ThreadPrintRange(200,299);
        t2.setName("Thread200to299");
        Thread t3 = new ThreadPrintRange(300,399);
        t3.setName("Thread300to399");
        nextThreadRunCode=100;
        t2.start();
        t1.start();
        t3.start();
    }
    private static class ThreadPrintRange extends Thread {

        int startRange,endRange;
        public ThreadPrintRange(int startRange, int endRange)
        {
            this.startRange = startRange;
            this.endRange = endRange;
        }

        @Override
        public void run() {

            while (true) {
                try {
                    if (!lock.tryLock()) {
                        lock.lock();

                        for (int i = startRange; i <= endRange; i++) {

                            while (! (nextThreadRunCode == startRange)) {
                                try {
                                    cond.await();
                                } catch (InterruptedException e) {
                                    e.printStackTrace();
                                }
                            }

                            System.out.println(Thread.currentThread().getName() + ":" + i);
                            nextThreadRunCode = getNextThreadRunCode(startRange);
                            cond.signalAll();
                        }
                    }
                } finally {
                    lock.unlock();
                }
            }
        }

        private int getNextThreadRunCode(int startRange) {

            if (startRange == 100)
            {
                return 200;
            }
            else if (startRange == 200) {
                return 300;
            }
            else return 100;
        }
    }
}