生产者消费者模型

生产者消费者模型

今天刷面经看到有人被问到手撕生产者消费者,所以顺手写一下熟悉一下流程

public class ProducerAndConsumer {
  private static final ReentrantLock lock = new ReentrantLock();
  private static final Condition empty = lock.newCondition(), full = lock.newCondition();
  private static volatile int cnt = 0;
  private static final int N = 10;
  private static final int MAX_CNT = 30;

  private static void add() {
    cnt++;
  }

  private static void get() {
    cnt--;
  }

  public static void main(String[] args) {
    Thread[] cons = new Thread[10], pros = new Thread[10];
    for (int i = 0; i < N * 100; i++) {
      new Thread(() -> {
        lock.lock();
        try {
          while (cnt == 0) {
            empty.await();
          }
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
        System.out.println("[ CONSUMER " + Thread.currentThread().getName() + " ] => Now cnt = "
            + cnt + ", Then cnt-- = " + (cnt - 1));
        get();
        full.signal();
        lock.unlock();
      }).start();

      new Thread(() -> {
        lock.lock();
        try {
          while (cnt == MAX_CNT) {
            full.await();
          }
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
        System.out.println("\033[1;31m[ PRODUCER " + Thread.currentThread().getName() + " ] => Now cnt = "
            + cnt + ", Then ++cnt = " + (cnt + 1) + "\033[0m");
        add();
        empty.signal();
        lock.unlock();
      }).start();
    }
  }
}

线程交替打印模型

public class ThreadDo {
  private static volatile int idx = 0;
  private static volatile boolean st = false;
  private static Object lock = new Object();

  private static Thread t1, t2;

  private static void sync() {
    idx = 0;
    t1 = new Thread(() -> {
      while (idx < 30) {
        synchronized (lock) {
          if (idx % 2 == 0) {
            System.out.println("[ " + Thread.currentThread().getName() + " ] => Now idx = " + idx + ", ++idx = " + ++idx);
          }
        }
      }
    });
    t2 = new Thread(() -> {
      while (idx < 30) {
        synchronized (lock) {
          if (idx % 2 == 1) {
            System.out.println("\033[1;31m[ " + Thread.currentThread().getName() + " ] => Now idx = " + idx + ", ++idx = " + ++idx + "\033[0m");
          }
        }
      }
    });
    t1.start();
    t2.start();
  }

  private static void booleanCor() {
    idx = 0;
    t1 = new Thread(() -> {
      while (idx < 30) {
        if (!st) {
          System.out.println("\033[1;31m[ " + Thread.currentThread().getName() + " ] => Now idx = " + idx + ", ++idx = " + ++idx + "\033[0m");
          st = true;
        }
      }
    });
    t2 = new Thread(() -> {
      while (idx < 30) {
        if (st) {
          System.out.println("[ " + Thread.currentThread().getName() + " ] => Now idx = " + idx + ", ++idx = " + ++idx);
          st = false;
        }
      }
    });
    t1.start(); t2.start();
  }

  public static void main(String[] args) {
    booleanCor();
    sync();
  }
}