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:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
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">
<Button
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"
/>
</android.support.constraint.ConstraintLayout>
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。
