作为程序猿必须了解的生产者与消费者

分手后的思念是犯贱 2023-10-03 11:46 25阅读 0赞

### JUC并发编程三：生产者与消费者（Java） ###

面试：单例模式，排序算法，生产者与消费者，死锁

代码示例：

package PC;
    
    /*
    线程之间的通信问题：生产者与消费者问题!  等待唤醒，通知唤醒
    线程交替执行  A  B 操作同一个变量 num=0
    A num+1
    B num-1
     */
    public class A {
        
        public static void main(String[] args) {
        
            Data data=new Data();
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    try {
        
                        data.increament();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                      }
            },"A").start();
    
          new Thread(()->{
        
              for (int i = 0; i < 10; i++) {
        
                  try {
        
                      data.decreament();
                  } catch (InterruptedException e) {
        
                      e.printStackTrace();
                  }
                      }
                },"B").start();
    
        }
    }
    
    
    //判断等待，业务，通知
    class  Data{
          //数字 资源类
        private int number=0;
    
        //+1
        public synchronized void increament() throws InterruptedException {
        
            if(number!=0){
        
                //等待
                this.wait();
            }
            number++;
            System.out.println(Thread.currentThread().getName()+"=>"+number);
            //通知其他线程，+1完毕
            this.notifyAll();
    
        }
    
        //-1
        public synchronized void decreament() throws InterruptedException {
        
            if(number==0){
        
                //等待
                this.wait();
            }
            number--;
            System.out.println(Thread.currentThread().getName()+"=>"+number);
            //通知其他线程，+1完毕
            this.notifyAll();
    
        }
    }

问题存在：A、B、C、D四个线程！

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这里将if改为while判断即可

代码示例1：

package PC;
    
    /*
    线程之间的通信问题：生产者与消费者问题!  等待唤醒，通知唤醒
    线程交替执行  A  B 操作同一个变量 num=0
    A num+1
    B num-1
     */
    public class A {
        
        public static void main(String[] args) {
        
            Data data=new Data();
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    try {
        
                        data.increament();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                      }
            },"A").start();
    
          new Thread(()->{
        
              for (int i = 0; i < 10; i++) {
        
                  try {
        
                      data.decreament();
                  } catch (InterruptedException e) {
        
                      e.printStackTrace();
                  }
                      }
                },"B").start();
    
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    try {
        
                        data.increament();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
            },"C").start();
    
    
    
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    try {
        
                        data.decreament();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
            },"D").start();
    
        }
    }
    
    
    //判断等待，业务，通知
    class  Data{
          //数字 资源类
        private int number=0;
    
        //+1
        public synchronized void increament() throws InterruptedException {
        
            while(number!=0){
        
                //等待
                this.wait();
            }
            number++;
            System.out.println(Thread.currentThread().getName()+"=>"+number);
            //通知其他线程，+1完毕
            this.notifyAll();
    
        }
    
        //-1
        public synchronized void decreament() throws InterruptedException {
        
            while(number==0){
        
                //等待
                this.wait();
            }
            number--;
            System.out.println(Thread.currentThread().getName()+"=>"+number);
            //通知其他线程，+1完毕
            this.notifyAll();
    
        }
    }

代码示例2：

package PC;
    
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    
    public class B {
        
        public static void main(String[] args) {
        
            Data2 data=new Data2();
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    try {
        
                        data.increament();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
            },"A").start();
    
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    try {
        
                        data.decreament();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
            },"B").start();
    
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    try {
        
                        data.increament();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
            },"C").start();
    
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    try {
        
                        data.decreament();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
            },"D").start();
    
        }
    }
    
    
    
    //判断等待，业务，通知
    class  Data2{
          //数字 资源类
        private int number=0;
        Lock lock=new ReentrantLock();
        Condition condition = lock.newCondition();
                //condition.await();  //等待
                //condition.signalAll(); //唤醒全部
        //+1
        public void increament() throws InterruptedException {
        
            lock.lock();
            try {
        
                //业务代码
                while(number!=0){
        
                    //等待
                    condition.await();
                }
                number++;
                System.out.println(Thread.currentThread().getName()+"=>"+number);
                //通知其他线程，+1完毕
               condition.signalAll();
            } catch (Exception e) {
        
                e.printStackTrace();
            } finally {
        
                lock.unlock();
            }
    
        }
        //-1
        public void decreament() throws InterruptedException {
        
            lock.lock();
            try {
        
                while(number==0){
        
                    //等待
                    condition.await();
                }
                number--;
                System.out.println(Thread.currentThread().getName()+"=>"+number);
                //通知其他线程，+1完毕
                condition.signalAll();
            } catch (Exception e) {
        
                e.printStackTrace();
            } finally {
        
                lock.unlock();
            }
    
    
        }
    }

代码示例3：

package PC;
    
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    /*
    A执行完调用B，B执行完调用C，C执行完调用A
     */
    
    public class C {
        
        public static void main(String[] args) {
        
            Data3 data=new Data3();
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    data.printA();
                }
            },"A").start();
    
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    data.printB();
                }
            },"B").start();
    
            new Thread(()->{
        
                for (int i = 0; i < 10; i++) {
        
                    data.printC();
                }
            },"C").start();
    
        }
    }
    
    class Data3{
         //资源类 Lock
        private Lock lock=new ReentrantLock();
        private Condition condition1 = lock.newCondition();
        private Condition condition2 = lock.newCondition();
        private Condition condition3 = lock.newCondition();
        private int number=1;
        //number为1的时候，A执行
        //number为2的时候，B执行
        //number为3的时候，C执行
        public  void printA(){
        
            lock.lock();
            try {
        
                //业务代码  判断-》执行-》通知
                while(number!=1){
        
                    //等待
                    condition1.await();
                }
                System.out.println(Thread.currentThread().getName()+"AAAAAA");
                //唤醒，唤醒指定的人,-->B
                number=2;
                condition2.signal();
    
            } catch (Exception e) {
        
                e.printStackTrace();
            } finally {
        
                lock.unlock();
            }
        }
        public  void printB(){
        
            lock.lock();
            try {
        
                //业务代码  判断-》执行-》通知
                while(number!=2){
        
                    condition2.await();
                }
                System.out.println(Thread.currentThread().getName()+"BBBBBB");
                number=3;
                condition3.signal();
            } catch (Exception e) {
        
                e.printStackTrace();
            } finally {
        
                lock.unlock();
            }
        }
    
        public  void printC(){
        
            lock.lock();
            try {
        
                //业务代码  判断-》执行-》通知
                while(number!=3){
        
                    condition3.await();
                }
                System.out.println(Thread.currentThread().getName()+"CCCCCC");
                number=1;
                condition1.signal();
            } catch (Exception e) {
        
                e.printStackTrace();
            } finally {
        
                lock.unlock();
            }
        }
    }
         //业务代码  判断-》执行-》通知
                while(number!=3){
        
                    condition3.await();
                }
                System.out.println(Thread.currentThread().getName()+"CCCCCC");
                number=1;
                condition1.signal();
            } catch (Exception e) {
        
                e.printStackTrace();
            } finally {
        
                lock.unlock();
            }
        }
    }