在 Java 中使用两个线程打印偶数和奇数

multithreading java synchronization

2022-09-01 21:30:43

我尝试了下面的代码。我从其他一些帖子中获取了这段代码，根据作者的说法，这是正确的。但是当我尝试跑步时，它并没有给我确切的结果。

这主要是按顺序打印偶数和奇数值。

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();
    }

}

有人可以帮我解决这个问题吗？

编辑预期结果：奇数：1 偶数：2 奇数：3 偶数：4 奇数：5 偶数：6 奇数：7 偶数：8 奇数：9

答案 1

找到解决方案。寻找此问题解决方案的人可以参考：-）

public class PrintEvenOddTester {

    public static void main(String... args) {
        Printer print = new Printer();
        Thread t1 = new Thread(new TaskEvenOdd(print, 10, false));
        Thread t2 = new Thread(new TaskEvenOdd(print, 10, true));
        t1.start();
        t2.start();
    }

}

class TaskEvenOdd implements Runnable {

    private int max;
    private Printer print;
    private boolean isEvenNumber;

    TaskEvenOdd(Printer print, int max, boolean isEvenNumber) {
        this.print = print;
        this.max = max;
        this.isEvenNumber = isEvenNumber;
    }

    @Override
    public void run() {

        //System.out.println("Run method");
        int number = isEvenNumber == true ? 2 : 1;
        while (number <= max) {

            if (isEvenNumber) {
                //System.out.println("Even :"+ Thread.currentThread().getName());
                print.printEven(number);
                //number+=2;
            } else {
                //System.out.println("Odd :"+ Thread.currentThread().getName());
                print.printOdd(number);
                // number+=2;
            }
            number += 2;
        }

    }

}

class Printer {

    boolean isOdd = false;

    synchronized void printEven(int number) {

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

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

}

这给出了如下输出：

Odd:1
Even:2
Odd:3
Even:4
Odd:5
Even:6
Odd:7
Even:8
Odd:9
Even:10

答案 2

使用以下这个非常简单的 JAVA 8 可运行类功能

public class MultiThreadExample {

static AtomicInteger atomicNumber = new AtomicInteger(1);

public static void main(String[] args) {
    Runnable print = () -> {
        while (atomicNumber.get() < 10) {
            synchronized (atomicNumber) {
                if ((atomicNumber.get() % 2 == 0) && "Even".equals(Thread.currentThread().getName())) {
                    System.out.println("Even" + ":" + atomicNumber.getAndIncrement());
                } //else if ((atomicNumber.get() % 2 != 0) && "Odd".equals(Thread.currentThread().getName()))
                   else {System.out.println("Odd" + ":" + atomicNumber.getAndIncrement());
                }
            }
        }
    };

    Thread t1 = new Thread(print);
    t1.setName("Even");
    t1.start();
    Thread t2 = new Thread(print);
    t2.setName("Odd");
    t2.start();

}
}