多线程协调模板

Posted 2020-11-21 huanstephen

在多线程进行相互协调是个头疼的事，今天写个多线程协调操作模板，以后只要套用这个模板就好了

public abstract class Order implements Runnable {

    protected boolean open = true;
    
    protected ReentrantLock lock;
    
    protected Condition condition;
    
    protected static int STATUS = 0;

    public Order(ReentrantLock lock, Condition condition) {
        this.lock = lock;
        this.condition = condition;
    }

    public void run() {
        while (!Thread.interrupted() && this.open) {
            this.doSomething();
        }
    }
    
    private void doSomething() {
        this.lock.lock();
        
        try {
            while (this.getStatus() != STATUS) {
                try {
                    this.condition.await();
                    if (this.getStatus() != STATUS) {
                        this.doSomething();
                        return ;
                    }
                } catch (InterruptedException e) {
                    this.open = false;
                    return ;
                }
            }
            
            this.content();
            
            if (this.stop()) {
                return ;
            }
            
            STATUS = this.changeStatus();
            this.condition.signalAll();
        } finally {
            this.lock.unlock();
        }
    }
    
    public abstract int getStatus();
    
    public abstract void content();
    
    public abstract int changeStatus();
    
    public boolean stop() {
        return false;
    }
}

下面我们来测试一下，有这么一个需求，有三个线程，线程A输出三行OperateA，线程B输出两行OperateB，线程C输出一行OperateC，然后按照这种顺序循环三次。

测试示例：

public class ThreadOrderTest {

    public static class OperateA extends Order {

        public OperateA(ReentrantLock lock, Condition condition) {
            super(lock, condition);
        }

        @Override
        public int getStatus() {
            return 0;
        }

        @Override
        public void content() {
            for (int i = 0; i < 3; i ++) {
                System.out.println("OperateA");
            }
        }

        @Override
        public int changeStatus() {
            return 1;
        }
    }
    
    public static class OperateB extends Order {
        
        public OperateB(ReentrantLock lock, Condition condition) {
            super(lock, condition);
        }

        @Override
        public int getStatus() {
            return 1;
        }

        @Override
        public void content() {
            for (int i = 0; i < 2; i ++) {
                System.out.println("OperateB");
            }
        }

        @Override
        public int changeStatus() {
            return 2;
        }
    }
    
    public static class OperateC extends Order {

        private ExecutorService exec;
        
        private int max;
        
        public OperateC(ReentrantLock lock, Condition condition, ExecutorService exec, int max) {
            super(lock, condition);
            this.exec = exec;
            this.max = max;
        }

        @Override
        public int getStatus() {
            return 2;
        }

        @Override
        public void content() {
            System.out.println("OperateC");
        }

        @Override
        public int changeStatus() {
            return 0;
        }
        
        public boolean stop() {
            if (0 == --this.max) {
                this.open = false;
                this.exec.shutdownNow();
                return true;
            }
            return false;
        }
    }
    
    public static void main(String[] args) {
        ReentrantLock lock = new ReentrantLock();
        Condition condition = lock.newCondition();
        
        ExecutorService exec = Executors.newCachedThreadPool();
        exec.execute(new OperateB(lock, condition));
        exec.execute(new OperateC(lock, condition, exec, 3));
        exec.execute(new OperateA(lock, condition));
    }

}

输出：

OperateA
OperateA
OperateA
OperateB
OperateB
OperateC
OperateA
OperateA
OperateA
OperateB
OperateB
OperateC
OperateA
OperateA
OperateA
OperateB
OperateB
OperateC