前言

Java中实现多线程主要由以下两种方式:继承Thread类和实现Runnable接口，本文主要说明Runnable接口实现多线程。

Runnable接口简介

(1)定义

Runnable接口是线程辅助类，仅定义了一个方法run()方法

(2)作用

实现多线程

(3)优点

灵活：Runnable可以继承其他类实现对Runnable实现类的增强，避免了Thread类由于继承Thread类而无法继承其他类的问题

共享资源:Runnable接口的run()方法可以被多个线程共享，适用于多个进程处理一种资源的问题

使用方法

(1) 实现Runnable接口

(2) 重写run()方法

(3) 创建runnable实例

(4) 创建Thread实例

(5) 将Runnable实例放入Thread实例中

(6) 通过线程实例控制线程的行为(运行，停止)，在运行时会调用Runnable接口中的run方法。

注意:Java中真正能创建新线程的只有Thread类对象

通过实现Runnable的方式，最终还是通过Thread类对象来创建线程

Runnable方式也分为标准方式和匿名方式

(1)标准方式

public class MainActivity extends AppCompatActivity {

Button btn;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

btn = findViewById(R.id.btn);

//2.创建MyRunnable实例

MyRunnable runnable=new MyRunnable();

//3.创建Thread对象

//4.将MyRunnable放入Thread实例中

Thread thread=new Thread(runnable);

//5.通过线程对象操作线程(运行、停止)

thread.start();

}

//1.实现runnable接口并重写run方法

class MyRunnable implements Runnable{

@Override

public void run() {

}

}

}

(2)匿名方式

public class MainActivity extends AppCompatActivity {

Button btn;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

//1.匿名实现Runnable接口并重写run方法

Runnable runnable = new Runnable() {

@Override

public void run() {

}

};

//2.创建线程对象

//3.将runnable实例放入线程对象中

Thread thread=new Thread(runnable);

//4.由线程实例控制线程的行为(运行，停止)

thread.start();

}

}

实际用例

现在假设有两个窗口卖车票，每一秒卖出一张车票，每个窗口有100张票

activity_main.xml:

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

tools:context="com.zhqy.threaddemo.MainActivity">

android:id="@+id/btn"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

app:layout_constraintLeft_toLeftOf="parent"

app:layout_constraintRight_toRightOf="parent"

app:layout_constraintTop_toTopOf="parent"

app:layout_constraintBottom_toBottomOf="parent"

android:text="售票"

/>

MainActivity.java:

package com.zhqy.threaddemo;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

public class MainActivity extends AppCompatActivity {

Button btn;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

btn=findViewById(R.id.btn);

btn.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

//创建runnnable实例

TicketRunnable run1=new TicketRunnable();

TicketRunnable run2=new TicketRunnable();

//创建Thread实例并将runnable实例放入

Thread th1=new Thread(run1,"th1");

Thread th2=new Thread(run2,"th2");

//通过线程实例控制线程的行为(运行、停止)

th1.start();

th2.start();

}

});

}

//实现Runnable接口并重写run方法

class TicketRunnable implements Runnable{

int ticket=100;

@Override

public void run() {

//卖票

while (ticket>0){

Log.e(Thread.currentThread().getName(),"剩余票量:"+(--ticket));

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

}

}

测试结果:

08-26 10:52:21.954 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:99

08-26 10:52:21.954 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:99

08-26 10:52:22.955 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:98

08-26 10:52:22.955 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:98

08-26 10:52:23.955 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:97

08-26 10:52:23.955 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:97

08-26 10:52:24.956 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:96

08-26 10:52:24.956 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:96

08-26 10:52:25.956 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:95

08-26 10:52:25.956 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:95

08-26 10:52:26.957 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:94

08-26 10:52:26.957 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:94

08-26 10:52:27.958 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:93

08-26 10:52:27.958 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:93

08-26 10:52:28.958 10088-10241/com.zhqy.threaddemo E/th1: 剩余票量:92

08-26 10:52:28.958 10088-10242/com.zhqy.threaddemo E/th2: 剩余票量:92

那么如何让两个窗口共享“车票”呢？

package com.zhqy.threaddemo;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

public class MainActivity extends AppCompatActivity {

Button btn;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

btn=findViewById(R.id.btn);

btn.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

//创建runnnable实例

TicketRunnable run1=new TicketRunnable();

//创建Thread实例并将runnable实例放入

Thread th1=new Thread(run1,"th1");

Thread th2=new Thread(run1,"th2");

//通过线程实例控制线程的行为(运行、停止)

th1.start();

th2.start();

}

});

}

//实现Runnable接口并重写run方法

class TicketRunnable implements Runnable{

int ticket=100;

@Override

public void run() {

//卖票

while (ticket>0){

Log.e(Thread.currentThread().getName(),"剩余票量:"+(--ticket));

try {

Thread.sleep(1000);

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

}

}

这里看出两个线程公用了一个Runnable实现对象实例，这样两个线程就可以操作同一个共享资源--“车票”

测试结果

08-26 10:58:10.681 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:98

08-26 10:58:10.681 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:99

08-26 10:58:11.681 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:97

08-26 10:58:11.682 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:96

08-26 10:58:12.682 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:95

08-26 10:58:12.683 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:94

08-26 10:58:13.683 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:93

08-26 10:58:13.684 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:92

08-26 10:58:14.683 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:91

08-26 10:58:14.684 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:90

08-26 10:58:15.684 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:89

08-26 10:58:15.685 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:88

08-26 10:58:16.685 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:87

08-26 10:58:16.685 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:86

08-26 10:58:17.686 11641-11675/com.zhqy.threaddemo E/th2: 剩余票量:85

08-26 10:58:17.686 11641-11674/com.zhqy.threaddemo E/th1: 剩余票量:84

需要注意的是--线程同步问题

Thread与Runnable方式的对比

对比图.png

两种方式推荐使用实现Runnbale接口的方法，如果只想重写run方法也推荐使用实现Runnable接口的方式。

以上就是实现Runnbale接口实现多线程的全部内容。