java - 使用 3 个线程的多线程 Java

Question

我正在尝试创建一个使用线程的程序:线程 1 将整数放入列表中，线程 2 将偶数过滤到偶数列表中，线程 3 对奇数执行相同的操作。

public class Manage {

private Object lock = new Object();
private LinkedList<Integer> intStorage = new LinkedList<Integer>();
private LinkedList<Integer> evens = new LinkedList<>();
private LinkedList<Integer> odds = new LinkedList<>();

public void intCollection() throws InterruptedException {

    for (int i = 0; i <= 20; i++) {

        synchronized(lock) {    

            while(i == 20) {    
                lock.wait();
            }

            intStorage.add(i);
            lock.notifyAll();
            System.out.println(intStorage);
        }
        Thread.sleep(100);
    }
}

public void evens() throws InterruptedException {

    for(int i = 0; i < intStorage.size() ; i++) {

        synchronized(lock) {

            if(intStorage.get(i) % 2 != 0) {    
                lock.wait();
            }

            if(intStorage.get(i) % 2 == 0) {
                int j = intStorage.remove(i);
                evens.add(j);
                lock.notifyAll();
            }
            System.out.println(evens);
        }
        Thread.sleep(1000);
    }

}

public void odds() throws InterruptedException {

    for(int i = 0; i < intStorage.size() ; i++) {

        synchronized(lock) {

            if(intStorage.get(i) % 2 == 0) {    
                lock.wait();
            }

            if(intStorage.get(i) % 2 != 0) {
                int j = intStorage.remove(i);
                odds.add(j);
                lock.notifyAll();
            }
            System.out.println(odds);
        }
        Thread.sleep(1000);
    }

}

public static void main(String[] args) throws InterruptedException {

    Manager m = new Manager();

    Thread t1 = new Thread(){
        public void run() {
            try {
                m.intCollection();
            } catch (InterruptedException e) {
            }
        }
    };

    Thread t2 = new Thread(){
        public void run() {
            try {
                m.evens();
            } catch (InterruptedException e) {
            }
        }
    };
    Thread t3 = new Thread(){
        public void run() {
            try {
                m.odds();
            } catch (InterruptedException e) {
            }
        }
    };

    t1.start();
    t2.start();
    t3.start(); 

    t1.join();
    t2.join();
    t3.join();

}
}

线程 1 运行，但是我无法让线程 2 和线程 3 来过滤赔率和偶数。程序在线程 1 完成后终止。

Answer 1

这里的问题是您有三个线程竞争一个锁，但您需要 intCollection 线程首先赢得锁。如果任何其他线程首先赢得锁，您将由于该段而获得越界异常:

for(int i = 0; i < intStorage.size() ; i++) {

    synchronized(lock) {

        if(intStorage.get(i) % 2 == 0) {

即使 intStorage 为空，它也会调用 get(0) 并产生越界异常。

您也不需要通知和等待调用。我在我的解决方案中删除了那些。我添加了一个检查以查看 intStorage 是否为空，仅此而已。

完整答案如下:

import java.util.*;

public class Manager {

    private Object lock = new Object();
    private boolean running = true;
    private LinkedList<Integer> intStorage = new LinkedList<Integer>();
    private LinkedList<Integer> evens = new LinkedList<>();
    private LinkedList<Integer> odds = new LinkedList<>();

    public void intCollection() throws InterruptedException {

        for (int i = 0; i <= 20; i++) {

            synchronized(lock) {
                intStorage.add(i);
                System.out.println("storage: " + intStorage);
            }
            Thread.sleep(100);
        }
        running = false;
    }

    public void evens() throws InterruptedException {

        while( (!intStorage.isEmpty()) || running ) {
            synchronized (lock) {
                if(!intStorage.isEmpty()) {
                    if (intStorage.get(0) % 2 == 0) {
                        int j = intStorage.remove(0);
                        evens.add(j);
                    }
                    System.out.println("evens: " + evens);
                }
            }
            Thread.sleep(1);
        }

    }

    public void odds() throws InterruptedException {

        while( (!intStorage.isEmpty()) || running ) {
            synchronized (lock) {
                if(!intStorage.isEmpty()) {
                    if (intStorage.get(0) % 2 != 0) {
                        int j = intStorage.remove(0);
                        odds.add(j);
                    }
                    System.out.println("odds: " + odds);
                }
            }
            Thread.sleep(1);
        }

    }

    public static void main(String[] args) throws InterruptedException {

        //must be final to access
        final Manager m = new Manager();

        Thread t1 = new Thread(){
            public void run() {
                try {
                    m.intCollection();
                } catch (InterruptedException e) {
                }
            }
        };

        Thread t2 = new Thread(){
            public void run() {
                try {
                    m.evens();
                } catch (InterruptedException e) {
                }
            }
        };
        Thread t3 = new Thread(){
            public void run() {
                try {
                    m.odds();
                } catch (InterruptedException e) {
                }
            }
        };

        t1.start();
        t2.start();
        t3.start();

        t1.join();
        t2.join();
        t3.join();

    }
}