A classic interview question: Two threads, respectively print AB, among which thread A prints A, thread B prints B, prints 10 times each, so that the effect of ABABABA...
package com.shangshe.path; public class ThreadAB { /** * @param args */ public static void main(String[] args) { final Print business = new Print(); new Thread(new Runnable() { public void run() { for(int i=0;i<10;i++) { business.print_A(); } } } }).start(); new Thread(new Runnable() { public void run() { for(int i=0;i<10;i++) { business.print_B(); } } } }).start(); } } class Print { private boolean flag = true; public synchronized void print_A () { while(!flag) { try { this.wait(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.print("A"); flag = false; this.notify(); } public synchronized void print_B () { while(flag) { try { this.wait(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.print("B"); flag = true; this.notify(); } }From the above example, we can design a program with 3 threads or even n threads. The example given below is 3 threads, respectively, A, B, and C are printed 10 times, so that the effect of ABCABC..
public class ThreadABC { /** * @param args */ public static void main(String[] args) { final Print business = new Print(); new Thread(new Runnable() { public void run() { for(int i=0;i<100;i++) { business.print_A(); } } }).start(); new Thread(new Runnable() { public void run() { for(int i=0;i<100;i++) { business.print_B(); } } }).start(); new Thread(new Runnable() { public void run() { for(int i=0;i<100;i++) { business.print_C(); } } }).start(); }}class Print { private boolean should_a = true; private boolean should_b = false; private boolean should_c = false; public synchronized void print_A () { while(should_b || should_c) { try { this.wait(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.print("A"); should_a = false; should_b = true; should_c = false; this.notifyAll(); } public synchronized void print_B () { while(should_a || should_c) { try { this.wait(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.print("B"); should_a = false; should_b = false; should_c = true; this.notifyAll(); } public synchronized void print_C () { while(should_a || should_b) { try { this.wait(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.print("C"); should_a = true; should_b = false; should_c = false; this.notifyAll(); }}Once again, the importance of software engineering is proved; in multi-threaded programs, it should be said that in programs, we should put the business logic code into the same class to make it highly cohesive and low coupling