Java多线程基础

线程和进程的区别

线程是在进程内部做的事情。

线程的调用方式

继承Thread类

hero.java

java

package hero;
public class Hero {
    public String name;
    public float hp;
    public int damage;

    public void attackHero(Hero h){
        try{
            Thread.sleep(1000);
            h.hp = h.hp-this.damage;
            System.out.println(this.name+"攻击了"+h.name+"造成了"+this.damage+"点伤害");
        }catch (InterruptedException ie){
            ie.printStackTrace();
        }
        if(h.isDead()){
            System.out.println(h.name+"isDead!");
        }
    }
   public boolean isDead(){
        return hp<=0;
    }
}

ExtendsThreadKill.java

java

package ThreadTest1;
import hero.Hero;

public class ExtendsThreadKill extends Thread {
    private Hero h1;
    private Hero h2;

    ExtendsThreadKill(Hero h1, Hero h2){
        this.h1=h1;
        this.h2=h2;
    }

    public void run(){
        while(!h2.isDead()){
            h1.attackHero(h2);
        }
    }
}

测试类

java

import hero.Hero;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class ThreadTest {
    public List<Hero> GenerateHero(){
        String[] name = new String[]{"盖伦","盲僧","提莫","赏金"};
        List<Hero> heros = new ArrayList<>();
        for(int i=0;i<4;i++){
            Hero hero = new Hero();
            hero.name = name[i];
            hero.hp = new Random().nextFloat()*20;
            System.out.println(hero.name+"诞生，血量为"+hero.hp);
            hero.damage = new Random().nextInt(7);
            heros.add(hero);
        }
        return heros;
    }
    public static void main(String[] args) {
        List<Hero> hero = new ThreadTest().GenerateHero();
        ExtendsThreadKill th1 = new ExtendsThreadKill(hero.get(1),hero.get(0));
        ExtendsThreadKill th2 = new ExtendsThreadKill(hero.get(3),hero.get(2));
        th1.start();
        th2.start();
    }
}

实现Runnable接口

OverwriteRunnable.java

java

package ThreadTest2;

import hero.Hero;

public class OverwriteRunnable implements Runnable {

    private Hero h1;
    private Hero h2;

    public OverwriteRunnable(Hero h1, Hero h2){
        this.h1=h1;
        this.h2=h2;
    }
    @Override
    public void run() {
        while(!h2.isDead()){
            h1.attackHero(h2);
        }
    }
}

测试类

java

package ThreadTest2;

import ThreadTest1.ThreadTest;
import hero.Hero;

import java.util.List;

public class TestOverwriteRunnable {
    public static void main(String[] args) {
        List<Hero> h = new ThreadTest().GenerateHero();
        OverwriteRunnable o1 = new OverwriteRunnable(h.get(0),h.get(1));
        OverwriteRunnable o2 = new OverwriteRunnable(h.get(2),h.get(3));
        new Thread(o1).start();
        new Thread(o2).start();
    }
}

匿名类

在java8中，匿名类可以改写成lamda表达式

java

package ThreadTest3;

import ThreadTest1.ThreadTest;
import hero.Hero;

import java.util.List;

public class TestThread3 {
    public static void main(String[] args) {
        List<Hero> hs = new ThreadTest().GenerateHero();
        Thread t1 = new Thread(() -> {
            while (!hs.get(1).isDead()) {
                hs.get(2).attackHero(hs.get(1));
            }
        });

        Thread t2 = new Thread(() -> {
            while (!hs.get(0).isDead()) {
                hs.get(3).attackHero(hs.get(0));
            }
        });
        t1.start();
        t2.start();
    }

}

练习

遍历文件夹，若找到txt文件，则启动一个线程，将内容输出到控制台
FileReadThread.java

java

package practice;

import java.io.*;

public class FileReadThread extends Thread {
    private File f;

    FileReadThread(File file) {
        this.f = file;
    }

    public void run() {
        System.out.println(FindContent(f));
    }

    private String FindContent(File f) {
        try (FileReader fr = new FileReader(f)) {
            char [] content= new char[(int)f.length()];
            fr.read(content);
            fr.close();
            return new String(content);
        } catch (IOException e){
            e.printStackTrace();
            return null;
        }
    }

}

测试类

java

package practice;

import java.io.File;

public class TestFile {
    private void Search(File f){
        if(f!=null){
            if(f.isFile()){
                if(f.getName().endsWith(".txt")){
                    new FileReadThread(f).start();
                }
            }else if(f.isDirectory()){
                File[] files = f.listFiles();
                assert files != null;
                for(File file:files){
                    Search(file);
                }
            }
        }




    }
    public static void main(String[] args) {
        File f = new File("C:\\Users\\Jacob\\OneDrive\\Calibre");
        TestFile t = new TestFile();
        t.Search(f);
    }
}