Java Multithreading (producer consumer)

Turn https://www.oschina.net/code/snippet_111708_25438

This is a classic question, the essence of my solution is to abstract the problem into the producer consumer model, but it is a special producer consumer model, there are two requirements:
1, buffer size is 1 (with a Boolean variable to represent it)
2. The buffer is initially empty
More specifically, you can think of it as a printer that can only put one sheet of paper at a time, the thread that puts the paper is a, and the thread that prints is B. The initial state printer has no paper.

// 打印机类 public class Printer {           private boolean hasBufferToPrint = false ;   // 打印缓冲区是否有内容可以打印      // 打印A：相当于生产者，放一张纸      public synchronized void printA() {          while (hasBufferToPrint) {   // 缓冲区还有内容              try {                  wait();              } catch (InterruptedException e) {                  e.printStackTrace();              }          }                   System.out.print( "A" );          hasBufferToPrint = true ;                   notify();   // 唤醒打印B的线程      }           // 打印B：相当于消费者，消耗缓冲区中的纸，打印纸张      public synchronized void printB() {          while (!hasBufferToPrint) {              try {                  wait();              } catch (InterruptedException e) {                  e.printStackTrace();              }          }                   System.out.print( "B" );          hasBufferToPrint = false ;                   notify();   // 唤醒打印A的线程      }      static class ThreadA extends Thread {          private Printer printer;          public ThreadA(Printer printer) {              this .printer = printer;          }          public void run() {              for ( int i = 0 ; i < 10 ; i++) {                  printer.printA();              }          }      }      static class ThreadB extends Thread {          private Printer printer;                   public ThreadB(Printer printer) {              this .printer = printer;          }                   public void run() {              for ( int i = 0 ; i < 10 ; i++) {                  printer.printB();              }          }      }      public static void main(String args[]) {          Printer printer = new Printer();   // A、B线程共享同一个打印机          Thread a = new ThreadA(printer);          Thread b = new ThreadB(printer);                   a.start();          b.start();      } }

Java Multithreading (producer consumer)