1226-哲学家进餐

前言：学习JUC包后，通过leetcode多线程的题目练习一下,1226-哲学家进餐

Semaphore + ReentrantLock

最多允许4个哲学家就餐

public class DiningPhilosophers {
    private Semaphore max = new Semaphore(4);
    private ReentrantLock[] forkLocks = new ReentrantLock[5];

    public DiningPhilosophers() {
        for (int i = 0; i < 5; i++) {
            forkLocks[i] = new ReentrantLock();
        }
    }

    public void wantsToEat(int philosopher,
                           Runnable pickLeftFork,
                           Runnable pickRightFork,
                           Runnable eat,
                           Runnable putLeftFork,
                           Runnable putRightFork) throws InterruptedException {
        max.acquire();
        // 拿起左边叉子
        forkLocks[(philosopher + 1) % 5].lock();
        pickLeftFork.run();
        // 拿起右边叉子
        forkLocks[philosopher].lock();
        pickRightFork.run();
        // 吃
        eat.run();
        // 放下左边叉子
        putLeftFork.run();
        forkLocks[(philosopher + 1) % 5].unlock();
        // 放下右边叉子
        putRightFork.run();
        forkLocks[philosopher].unlock();
        max.release();
    }
}