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Java 多线程之间实现通讯

多线程 之间如何实现通讯

什么是多线程之间通讯? 线程 之间通讯,其实就是多个线程在操作同一个资源,但是操作的动作不同。画图演示 多线程之间通讯需求 需求:第一个线程写入(input)用户,另一个线程取读取(out)用户.实现读一个,写一个操作。

代码实现基本实现 共享资源源实体类

 class Res {
public String userSex;
public String userName;
}
  

输入线程资源

 class IntThrad extends Thread {
private Res res;

public IntThrad(Res res) {
this.res = res;
}

@Override
public void run() {
int count = 0;
while (true) {
if (count == 0) {
res.userName = "余胜军";
res.userSex = "男";
} else {
res.userName = "小紅";
res.userSex = "女";
}
count = (count + 1) % 2;
}
}
}

  

输出线程

 class OutThread extends Thread {
private Res res;

public OutThread(Res res) {
this.res = res;
}

@Override
public void run() {
while (true) {
System.out.println(res.userName + "--" + res.userSex);
}
}
}
  

运行代码

 Res res = new Res();
IntThrad intThrad = new IntThrad(res);
OutThread outThread = new OutThread(res);
intThrad.start();
outThread.start();
  

运行代码

注意:数据发生错乱,造成 线程安全 问题 解决线程安全问题 IntThrad 加上 synchronized

 class IntThrad extends Thread {
private Res res;

public IntThrad(Res res) {
this.res = res;
}

@Override
public void run() {
int count = 0;
while (true) {
synchronized (res) {
if (count == 0) {
res.userName = "余胜军";
res.userSex = "男";
} else {
res.userName = "小紅";
res.userSex = "女";
}
count = (count + 1) % 2;
}

}
}
}
  

输出线程加上synchronized

 class Res {
public String userName;
public String sex;
}

class InputThread extends Thread {
private Res res;

public InputThread(Res res) {
this.res = res;
}

@Override
public void run() {
int count = 0;
while (true) {
 synchronized (res) {
if (count == 0) {
res.userName = "余胜军";
res.sex = "男";
} else {
res.userName = "小红";
res.sex = "女";
}
count = (count + 1) % 2;
}

}
}
}

class OutThrad extends Thread {
private Res res;

public OutThrad(Res res) {
this.res = res;
}

@Override
public void run() {
while (true) {
synchronized (res) {
System.out.println(res.userName + "," + res.sex);
}
}

}
}

public class ThreadDemo01 {

public static void main(String[] args) {
Res res = new Res();
InputThread inputThread = new InputThread(res);
OutThrad outThrad = new OutThrad(res);
inputThread.start();
outThrad.start();
}

}

  

wait、notify方法

1.因为涉及到对象锁,他们必须都放在synchronized中来使用. Wait、Notify一定要在synchronized里面进行使用。2.Wait必须暂定当前正在执行的线程,并释放资源锁,让其他线程可以有机会运行3. notify/notifyall: 唤醒因锁池中的线程,使之运行

注意:一定要在线程同步中使用,并且是同一个锁的资源

 class Res {
public String userSex;
public String userName;
//线程通讯标识
public boolean flag =  false ;
}

  
 class IntThrad extends Thread {
private Res res;

public IntThrad(Res res) {
this.res = res;
}

@Override
public void run() {
int count = 0;
while (true) {
synchronized (res) {
if (res.flag) {
try {
   // 当前线程变为等待,但是可以释放锁
res.wait();
} catch (Exception e) {

}
}
if (count == 0) {
res.userName = "余胜军";
res.userSex = "男";
} else {
res.userName = "小紅";
res.userSex = "女";
}
count = (count + 1) % 2;
res.flag = true;
// 唤醒当前线程
res.notify();
}

}
}
}
  
 class OutThread extends Thread {
private Res res;

public OutThread(Res res) {
this.res = res;
}

@Override
public void run() {
while (true) {
synchronized (res) {
if (!res.flag) {
try {
res.wait();
} catch (Exception e) {
// TODO: handle exception
}
}
System.out.println(res.userName + "--" + res.userSex);
res.flag = false;
res.notify();
}
}
}
}
  
 public class ThreaCommun {
public static void main(String[] args) {
Res res = new Res();
IntThrad intThrad = new IntThrad(res);
OutThread outThread = new OutThread(res);
intThrad.start();
outThread.start();
}
}
  

wait与 sleep 区别

对于sleep()方法,我们首先要知道该方法是属于Thread类中的。而wait()方法,则是属于Object类中的。sleep()方法导致了程序暂停执行指定的时间,让出cpu该其他线程,但是他的监控状态依然保持者,当指定的时间到了又会自动恢复运行状态。在调用sleep()方法的过程中,线程不会释放对象锁。而当调用wait()方法的时候,线程会放弃对象锁,进入等待此对象的等待锁定池,只有针对此对象调用notify()方法后本线程才进入对象锁定池准备获取对象锁进入运行状态。

lock

在 jdk1.5 之后,并发包中新增了 Lock 接口(以及相关实现类)用来实现锁功能,Lock 接口提供了与 synchronized 关键字类似的同步功能,但需要在使用时手动获取锁和释放锁。 Lock写法

 Lock lock  = new ReentrantLock();
lock.lock();
try{
//可能会出现线程安全的操作
}finally{
//一定在finally中释放锁
//也不能把获取锁在try中进行,因为有可能在获取锁的时候抛出异常
  lock.ublock();
}

  

Lock与synchronized 关键字的区别 Lock 接口可以尝试非阻塞地获取锁 当前线程尝试获取锁。如果这一时刻锁没有被其他线程获取到,则成功获取并持有锁。Lock 接口能被中断地获取锁 与 synchronized 不同,获取到锁的线程能够响应中断,当获取到的锁的线程被中断时,中断异常将会被抛出,同时锁会被释放。Lock 接口在指定的截止时间之前获取锁,如果截止时间到了依旧无法获取锁,则返回。 Condition 用法 Condition的功能类似于在传统的线程技术中的,Object.wait()和Object.notify()的功能。 代码

 Condition condition = lock.newCondition();
res. condition.await();  类似wait
res. Condition.  signal () 类似notify
  
 class Res {
public String userName;
public String sex;
public boolean flag = false;
Lock lock = new ReentrantLock();
}

class InputThread extends Thread {
private Res res;
Condition newCondition;
public InputThread(Res res,Condition newCondition) {
this.res = res;
this.newCondition=newCondition;
}

@Override
public void run() {
int count = 0;
while (true) {
// synchronized (res) {

try {
res.lock.lock();
if (res.flag) {
try {
//res.wait();
newCondition.await();
} catch (Exception e) {
// TODO: handle exception
}
}
if (count == 0) {
res.userName = "余胜军";
res.sex = "男";
} else {
res.userName = "小红";
res.sex = "女";
}
count = (count + 1) % 2;
res.flag = true;
//res.notify();
newCondition.signal();
} catch (Exception e) {
// TODO: handle exception
}finally {
res.lock.unlock();
}
}

// }
}
}

class OutThrad extends Thread {
private Res res;
private Condition newCondition;
public OutThrad(Res res,Condition newCondition) {
this.res = res;
this.newCondition=newCondition;
}

@Override
public void run() {
while (true) {
//synchronized (res) {
try {
res.lock.lock();
if (!res.flag) {
try {
//res.wait();
newCondition.await();
} catch (Exception e) {
// TODO: handle exception
}
}
System.out.println(res.userName + "," + res.sex);
res.flag = false;
//res.notify();
newCondition.signal();
} catch (Exception e) {
// TODO: handle exception
}finally {
res.lock.unlock();
}
//}
}

}
}

public class ThreadDemo01 {

public static void main(String[] args) {
Res res = new Res();
Condition newCondition = res.lock.newCondition();
InputThread inputThread = new InputThread(res,newCondition);
OutThrad outThrad = new OutThrad(res,newCondition);
inputThread.start();
outThrad.start();
}

}
  

文章来源:智云一二三科技

文章标题:Java 多线程之间实现通讯

文章地址:https://www.zhihuclub.com/200134.shtml

关于作者: 智云科技

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