[图解Java]Condition

图解Condition

0. demo

我先给出一个demo, 这样大家就可以根据我给的这段代码, 边调试边看源码了. 还是那句话: 注意"My" , 我把ReentrantLock类改名为了 "MyReentrantLock"类 , "Lock"类改名为了"MyLock"类. 大家粘贴我的代码的时候, 把相应的"My"都去掉就好了, 否则会编译报错哦.

import java.util.Scanner;
import java.util.concurrent.locks.Condition;
import java.util.function.Supplier;

public class ConditionTest {
    static final Scanner scanner = new Scanner(System.in);
    static volatile String cmd = "";
    private static MyReentrantLock lock = new MyReentrantLock(true);
    private static Condition condition = lock.newCondition();

    public static void main(String[] args) {
        for (String name : new String[]{"w1", "w2", "w3", "w4", "w5", "w6"})
            new Thread(() -> func(() -> lock, name)).start();
        new Thread(() -> signalOne(() -> lock, "s")).start();

        while (scanner.hasNext()) {
            cmd = scanner.nextLine();
        }
    }

    public static void func(Supplier<MyLock> myLockSupplier, String name) {
        blockUntilEquals(() -> cmd, name);
        myLockSupplier.get().lock();

        System.out.println(name + "阻塞等待...");
        try {
            condition.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("释放了" + name);

        myLockSupplier.get().unlock();
    }

    public static void signalOne(Supplier<MyLock> myLockSupplier, String name) {
        while (true) {
            blockUntilEquals(() -> cmd, name);
            myLockSupplier.get().lock();
            condition.signal();
            System.out.println("通知唤醒了一个等待...");
            myLockSupplier.get().unlock();
        }
    }

    private static void blockUntilEquals(Supplier<String> cmdSupplier, final String expect) {
        while (!cmdSupplier.get().equals(expect))
            quietSleep(1000);
        clearCmd();
    }

    private static void quietSleep(int mills) {
        try {
            Thread.sleep(mills);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    private static void clearCmd() {
        cmd = "";
    }
}

使用例子在下面.

首先输入w1, 让线程1执行await() . 然后输入w2, 让线程2执行await(). 然后输入w3, 让线程3执行await().

接下来输入3次 s, 没输入一次s, 并按下回车, 就会signal通知一个await等待.