多线程综合实例
数字加减
【题目】设计四个线程对象，两个线程执行减操作，两个线程执行加操作。
class Resource{
//操作资源
private int num = 0; //进行加减操作的数据
private boolean flag = true; //加减切换，
//flag=true 表示可以进行加法，不能进行减法
public synchronized void add() throws Exception {
while(this.flag == false) {
//加法操作要等待
super.wait();
}
Thread.sleep(100);
this.num ++;
System.out.println("加法操作 - "+ Thread.currentThread().getName()+" - num = " + this.num);
this.flag = false; //加法执行完毕，需要执行减法
super.notifyAll(); //唤醒全部等待线程
}
public synchronized void sub() throws Exception {
while(this.flag == true) {
//减法操作需要等待
super.wait();
}
Thread.sleep(200);
this.num --;
System.out.println("减法操作 - "+ Thread.currentThread().getName()+" - num = " + this.num);
this.flag = true; //减法完成，需要执行加法
super.notifyAll(); //唤醒全部等待线程
}
}
class AddThread implements Runnable{
//加法线程
private Resource resource;
public AddThread(Resource resource) {
this.resource = resource;
}
@Override
public void run() {
for(int x =0; x<50; x++) {
try {
this.resource.add();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
class SubThread implements Runnable{
//减法线程
private Resource resource;
public SubThread(Resource resource) {
this.resource = resource;
}
@Override
public void run() {
for(int x =0; x<50; x++) {
try {
this.resource.sub();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
public class Num {
public static void main(String[] args) {
Resource res = new Resource();
AddThread at = new AddThread(res);
SubThread su = new SubThread(res);
new Thread(at,"加法线程 - A").start();
new Thread(at,"加法线程 - B").start();
new Thread(su,"减法线程 - X").start();
new Thread(su,"减法线程 - Y").start();
}
}
本题是一个经典的多线程开发操作，程序中要考虑的核心本质是：加一个、减一个，整体的计算结果应该只在0、1、-1之间循环出现。
生产电脑
【题目】设计一个生产电脑和搬运电脑类，要求生产出一台电脑就搬走一台电脑，如果没有新的电脑生产，则搬运工要等待；如果新电脑没有被搬走，则生产要等待，并统计生产电脑数量。
生产者消费者模型
class Computer{
private static int count = 0;
private String name;
private double price;
public Computer(String name, double price) {
this.name = name;
this.price = price;
this.count++;
}
@Override
public String toString() {
return "num = "+ count +" Computer [name=" + name + ", price=" + price + "]";
}
}
class Resources {
//
private Computer computer;
public synchronized void product() throws Exception{
if(this.computer != null) {
//已经生产过了
super.wait();
}
Thread.sleep(100);
this.computer = new Computer("lyz", 1.1);
System.out.println("生产电脑"+ this.computer);
super.notifyAll();
}
public synchronized void consume() throws Exception {
if(this.computer == null) {
//不能进行搬运
super.wait();
}
Thread.sleep(10);
this.computer = new Computer("lyz", 1.1);
super.notifyAll();
System.out.println("取走电脑"+this.computer);
this.computer = null; //已经取走了
super.notifyAll();
}
}
class Produced implements Runnable{
private Resources resource;
public Produced(Resources res) {
this.resource = res;
}
@Override
public void run() {
for(int x =0; x<50;x++) {
try {
this.resource.product();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
class Consum implements Runnable{
private Resources resource;
public Consum(Resources res) {
this.resource = res;
}
@Override
public void run() {
for(int x =0; x<50;x++) {
try {
this.resource.consume();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
public class ComputerDemo {
public static void main(String[] args) {
Resources res = new Resources();
new Thread(new Produced(res)).start();
new Thread(new Consum(res)).start();
}
}
竞争抢答
【题目】实现一个竞拍抢答程序，要求设置三个抢答者（三个线程），同时发出抢答指令，抢答成功或失败要给出提示。
这样一个多线程的操作由于里面需要牵扯到数据的返回问题，那么现在最好使用的Callable是比较方便的处理形式。
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
class AnswerThread implements Callable<String>{
private boolean flag = false;
@Override
public String call() throws Exception {
synchronized (this) {
if(this.flag == false) {
//抢答成功
this.flag = true;
return Thread.currentThread().getName() + "抢答成功";
} else {
return Thread.currentThread().getName() + "抢答失败";
}
}
}
}
public class AnswerDemo {
public static void main(String[] args) throws Exception{
AnswerThread mt = new AnswerThread();
FutureTask<String> taskA = new FutureTask<String>(mt);
FutureTask<String> taskB = new FutureTask<String>(mt);
FutureTask<String> taskC = new FutureTask<String>(mt);
new Thread(taskA, "A").start();
new Thread(taskB, "B").start();
new Thread(taskC, "C").start();
System.out.println(taskA.get());
System.out.println(taskB.get());
System.out.println(taskC.get());
}
}