生产者和消费者问题 生产者和消费者问题package com.sw.pc; /** * @Author suaxi * @Date 2021/1/4 14:25 */ public class A { public static void main(String[] args) { Data data = new Data(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data.incr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"A").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data.decr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"B").start(); } } class Data{ private int num = 0; //+1 public synchronized void incr() throws InterruptedException { if (num!=0){ //等待 this.wait(); } num++; System.out.println(Thread.currentThread().getName()+"===>"+num); //通知 this.notifyAll(); } //-1 public synchronized void decr() throws InterruptedException { if (num==0){ //等待 this.wait(); } num--; System.out.println(Thread.currentThread().getName()+"===>"+num); //通知 this.notifyAll(); } } 当增加多个线程时（A，B，C，D），会出现虚假唤醒的问题虚假唤醒：线程可以被唤醒，但不会被通知、中断或超时解决方法：将if判断换为whilepackage com.sw.pc; /** * @Author suaxi * @Date 2021/1/4 14:25 */ public class A { public static void main(String[] args) { Data data = new Data(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data.incr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"A").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data.decr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"B").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data.incr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"C").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data.decr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"D").start(); } } class Data{ private int num = 0; //+1 public synchronized void incr() throws InterruptedException { while (num!=0){ //等待 this.wait(); } num++; System.out.println(Thread.currentThread().getName()+"===>"+num); //通知 this.notifyAll(); } //-1 public synchronized void decr() throws InterruptedException { while (num==0){ //等待 this.wait(); } num--; System.out.println(Thread.currentThread().getName()+"===>"+num); //通知 this.notifyAll(); } } JUC版生产者消费者问题使用了Condition接口下的await()等待和signalAll()通知package com.sw.pc; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; /** * @Author suaxi * @Date 2021/1/4 14:55 */ public class B { public static void main(String[] args) { Data1 data1 = new Data1(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data1.incr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"A").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data1.decr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"B").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data1.incr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"C").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { try { data1.decr(); } catch (InterruptedException e) { e.printStackTrace(); } } },"D").start(); } } class Data1{ private int num = 0; Lock lock = new ReentrantLock(); Condition condition = lock.newCondition(); //+1 public void incr() throws InterruptedException { try { lock.lock(); //加锁 while (num!=0){ //等待 condition.await(); } num++; System.out.println(Thread.currentThread().getName()+"===>"+num); //通知 condition.signalAll(); } catch (Exception e) { e.printStackTrace(); } finally { lock.unlock(); //解锁 } } //-1 public void decr() throws InterruptedException { try { lock.lock(); //加锁 while (num==0){ //等待 condition.await(); } num--; System.out.println(Thread.currentThread().getName()+"===>"+num); //通知 condition.signalAll(); } catch (Exception e) { e.printStackTrace(); } finally { lock.unlock(); //解锁 } } }Condition精准通知与线程唤醒可以看到之前的线程执行顺序是无序的。package com.sw.pc; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; /** * @Author suaxi * @Date 2021/1/4 15:08 * Condition精准通知与线程唤醒 * ABC三个人互相打电话，A->B,B->C,C->A顺序执行 */ public class C { public static void main(String[] args) { Data2 data2 = new Data2(); new Thread(() ->{ for (int i = 0; i < 10; i++) { data2.CallA(); } },"A").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { data2.CallB(); } },"B").start(); new Thread(() ->{ for (int i = 0; i < 10; i++) { data2.CallC(); } },"C").start(); } } class Data2{ private int num = 1; // 1A 2B 3C private Lock lock = new ReentrantLock(); Condition condition1 = lock.newCondition(); Condition condition2 = lock.newCondition(); Condition condition3 = lock.newCondition(); public void CallA(){ try { lock.lock(); //加锁 while (num!=1){ //等待 condition1.await(); } num = 2; System.out.println(Thread.currentThread().getName()+"===>A打完了"); //通知 condition2.signal(); } catch (Exception e) { e.printStackTrace(); } finally { lock.unlock(); //解锁 } } public void CallB(){ try { lock.lock(); //加锁 while (num!=2){ //等待 condition2.await(); } num = 3; System.out.println(Thread.currentThread().getName()+"===>B打完了"); //通知 condition3.signal(); } catch (Exception e) { e.printStackTrace(); } finally { lock.unlock(); //解锁 } } public void CallC(){ try { lock.lock(); //加锁 while (num!=3){ //等待 condition3.await(); } num = 1; System.out.println(Thread.currentThread().getName()+"===>C打完了"); //通知 condition1.signal(); } catch (Exception e) { e.printStackTrace(); } finally { lock.unlock(); //解锁 } } } 通过不同的监视器监视线程来达到精准通知与线程唤醒的目的