如何使用Java中的两个线程输出偶数和奇数?

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我用了以下的代码,主要为了按顺序输出偶数和奇数,但是没有输出正确的结果

public class PrintEvenOddTester {



    public static void main(String ... args){
        Printer print = new Printer(false);
        Thread t1 = new Thread(new TaskEvenOdd(print));
        Thread t2 = new Thread(new TaskEvenOdd(print));
        t1.start();
        t2.start();
    }


}



class TaskEvenOdd implements Runnable {

    int number=1;
    Printer print;

    TaskEvenOdd(Printer print){
        this.print = print;
    }

    @Override
    public void run() {

        System.out.println("Run method");
        while(number<10){

            if(number%2 == 0){
                System.out.println("Number is :"+ number);
                print.printEven(number);
                number+=2;
            }
            else {
                System.out.println("Number is :"+ number);
                print.printOdd(number);
                number+=2;
            }
        }

      }

    }

class Printer {

    boolean isOdd;

    Printer(boolean isOdd){
        this.isOdd = isOdd;
    }

    synchronized void printEven(int number) {

        while(isOdd){
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("Even:"+number);
        isOdd = true;
        notifyAll();
    }

    synchronized void printOdd(int number) {
        while(!isOdd){
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("Odd:"+number);
        isOdd = false;
        notifyAll();
    }

}

有人能帮我解决这个问题吗?

预期输出结果:奇数:1偶数:2奇偶:3偶数:4奇数:5偶数:6奇数:7偶数:8奇数:9偶数

提问于
用户回答回答于

可以消除“偶数或奇数”问题,并使用wait/notify结构:

public class WaitNotifyDemoEvenOddThreads {
    /**
     * A transfer object, only use with proper client side locking!
     */
    static final class LastNumber {
        int num;
        final int limit;

        LastNumber(int num, int limit) {
            this.num = num;
            this.limit = limit;
        }
    }

    static final class NumberPrinter implements Runnable {
        private final LastNumber last;
        private final int init;

        NumberPrinter(LastNumber last, int init) {
            this.last = last;
            this.init = init;
        }

        @Override
        public void run() {
            int i = init;
            synchronized (last) {
                while (i <= last.limit) {
                    while (last.num != i) {
                        try {
                            last.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    System.out.println(Thread.currentThread().getName() + " prints: " + i);
                    last.num = i + 1;
                    i += 2;
                    last.notify();
                }
            }
        }
    }

    public static void main(String[] args) {
        LastNumber last = new LastNumber(0, 10); // or 0, 1000
        NumberPrinter odd = new NumberPrinter(last, 1);
        NumberPrinter even = new NumberPrinter(last, 0);
        new Thread(odd, "o").start();
        new Thread(even, "e").start();
    }
}
用户回答回答于
Simpler Version in Java 8:

public class EvenOddPrinter {
    static boolean flag = true;
    public static void main(String[] args) {
        Runnable odd = () -> {
            for (int i = 1; i <= 10;) {
                if(EvenOddPrinter.flag) {
                    System.out.println(i);
                    i+=2;
                    EvenOddPrinter.flag = !EvenOddPrinter.flag;
                }
            }
        };

        Runnable even = () -> {
            for (int i = 2; i <= 10;) {
                if(!EvenOddPrinter.flag) {
                    System.out.println(i);
                    i+=2;
                    EvenOddPrinter.flag = !EvenOddPrinter.flag;
                }
            }
        };

         Thread t1 = new Thread(odd, "Odd");
         Thread t2 = new Thread(even, "Even");
         t1.start();
         t2.start();
    }
}

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