Multithreading series teaching materials （ one ）- Java There are three ways to create a thread

Multithreading series teaching materials （ two ）- Java Common threading methods

Multithreading means that at the same time , Can do many things .

Creating multithreading has 3 Two ways , namely Inherit thread class , realization Runnable Interface , Anonymous class

Correct

This video is interpretive , So I hope you have read the content of this knowledge point , And after writing the corresponding code , Watch with questions , Only in this way can we gain more . It is not recommended to watch the video at the beginning

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Step 1 : Thread concept
Step 2 : Create multithreaded - Inherit thread class
Step 3 : Create multithreaded - realization Runnable Interface
Step 4 : Create multithreaded - Anonymous class
Step 5 : There are three ways to create multithreading
Step 6 : practice - Find file contents synchronously
Step 7 : answer - Find file contents synchronously

Step 1 :

Thread concept

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First, understand the process (Processor) And threads (Thread) The difference between
Process ： Start a LOL.exe It's called a process . Then start another DOTA.exe, This is called two processes .
Thread ： Threads are things that are done simultaneously within a process , For example, in LOL in , There are many things to do at the same time , For example " Galen ” Kill “ Timo ”, At the same time “ Bounty Hunter ” Killing again “ Blind monk ”, This is achieved by multithreading .

The code here demonstrates Without multithreading ：
Only after Galen killed Timo , Bounty hunters began to kill blind monks

Hero.java
TestThread.java

More lines of code , Please click to view

package charactor;

import java.io.Serializable;
 
public class Hero{
    public String name; 
    public float hp;
    
    public int damage;
    
    public void attackHero(Hero h) {
    	try {
    		// To show that the attack takes time , Every attack is suspended 1000 millisecond 
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
    	h.hp-=damage;
    	System.out.format("%s  Attacking  %s, %s My blood became  %.0f%n",name,h.name,h.name,h.hp);
    	
    	if(h.isDead())
    		System.out.println(h.name +" Dead ！");
    }

	public boolean isDead() {
		return 0>=hp?true:false;
	}

}

More lines of code , Please click to view

package multiplethread;

import charactor.Hero;

public class TestThread {

	public static void main(String[] args) {
		
		Hero gareen = new Hero();
		gareen.name = " Galen ";
		gareen.hp = 616;
		gareen.damage = 50;

		Hero teemo = new Hero();
		teemo.name = " Timo ";
		teemo.hp = 300;
		teemo.damage = 30;
		
		Hero bh = new Hero();
		bh.name = " Bounty Hunter ";
		bh.hp = 500;
		bh.damage = 65;
		
		Hero leesin = new Hero();
		leesin.name = " Blind monk ";
		leesin.hp = 455;
		leesin.damage = 80;
		
		// Galen attacked Timo 
		while(!teemo.isDead()){
			gareen.attackHero(teemo);
		}

		// Bounty hunters attack blind monks 
		while(!leesin.isDead()){
			bh.attackHero(leesin);
		}
	}
	
}

Step 2 :

Create multithreaded - Inherit thread class

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Use multithreading , You can do what Galen is attacking Timo At the same time , Bounty hunters are also attacking blind monks
Design a class KillThread Inherit Thread, And rewrite run method
Start thread method ： Instantiate a KillThread Object , And call its start method
You can observe The bounty hunter attacked the blind monk At the same time , Galen is also attacking Timo

Create multithreaded - Inherit thread class

KillThread.java
TestThread.java

More lines of code , Please click to view

package multiplethread;

import charactor.Hero;

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

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

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

More lines of code , Please click to view

package multiplethread;

import charactor.Hero;

public class TestThread {

	public static void main(String[] args) {
		
		Hero gareen = new Hero();
		gareen.name = " Galen ";
		gareen.hp = 616;
		gareen.damage = 50;

		Hero teemo = new Hero();
		teemo.name = " Timo ";
		teemo.hp = 300;
		teemo.damage = 30;
		
		Hero bh = new Hero();
		bh.name = " Bounty Hunter ";
		bh.hp = 500;
		bh.damage = 65;
		
		Hero leesin = new Hero();
		leesin.name = " Blind monk ";
		leesin.hp = 455;
		leesin.damage = 80;
		
		KillThread killThread1 = new KillThread(gareen,teemo);
		killThread1.start();
		KillThread killThread2 = new KillThread(bh,leesin);
		killThread2.start();
		
	}
	
}

Step 3 :

Create multithreaded - realization Runnable Interface

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Create class Battle, realization Runnable Interface
When starting , First create a Battle Object , Then according to the battle Object to create a thread object , And start

Battle battle1 = new Battle(gareen,teemo);
new Thread(battle1).start();

battle1 Object implements Runnable Interface , So there are run method , But call directly run method , Does not start a new thread .
must , With the help of a thread object start() method , Will start a new thread .
So , In creating Thread Object time , hold battle1 Pass it in as a parameter of the constructor , When this thread starts , Will execute battle1.run() The method is .

Battle.java
TestThread.java

More lines of code , Please click to view

package multiplethread;

import charactor.Hero;

public class Battle implements Runnable{
	
	private Hero h1;
	private Hero h2;

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

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

More lines of code , Please click to view

package multiplethread;

import charactor.Hero;

public class TestThread {

	public static void main(String[] args) {
		
		Hero gareen = new Hero();
		gareen.name = " Galen ";
		gareen.hp = 616;
		gareen.damage = 50;

		Hero teemo = new Hero();
		teemo.name = " Timo ";
		teemo.hp = 300;
		teemo.damage = 30;
		
		Hero bh = new Hero();
		bh.name = " Bounty Hunter ";
		bh.hp = 500;
		bh.damage = 65;
		
		Hero leesin = new Hero();
		leesin.name = " Blind monk ";
		leesin.hp = 455;
		leesin.damage = 80;
		
		Battle battle1 = new Battle(gareen,teemo);
		
		new Thread(battle1).start();

		Battle battle2 = new Battle(bh,leesin);
		new Thread(battle2).start();

	}
	
}

Step 4 :

Create multithreaded - Anonymous class

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Correct ask

use Anonymous class , Inherit Thread, rewrite run method , Directly in run Write business code in method
One advantage of anonymous classes is that they can easily access external local variables .
The premise is that external local variables need to be declared as final.(JDK7 It won't be needed in the future )

More lines of code , Please click to view

package multiplethread;
 
import charactor.Hero;
 
public class TestThread {
 
    public static void main(String[] args) {
         
        Hero gareen = new Hero();
        gareen.name = " Galen ";
        gareen.hp = 616;
        gareen.damage = 50;
 
        Hero teemo = new Hero();
        teemo.name = " Timo ";
        teemo.hp = 300;
        teemo.damage = 30;
         
        Hero bh = new Hero();
        bh.name = " Bounty Hunter ";
        bh.hp = 500;
        bh.damage = 65;
         
        Hero leesin = new Hero();
        leesin.name = " Blind monk ";
        leesin.hp = 455;
        leesin.damage = 80;
         
        // Anonymous class 
        Thread t1= new Thread(){
            public void run(){
                // External local variables are used in anonymous classes teemo, We must put teemo Declare as final
            	// But in JDK7 in the future , You don't have to add final Yes 
                while(!teemo.isDead()){
                    gareen.attackHero(teemo);
                }               
            }
        };
        
        t1.start();
         
        Thread t2= new Thread(){
            public void run(){
                while(!leesin.isDead()){
                    bh.attackHero(leesin);
                }               
            }
        };
        t2.start();
        
    }
     
}

Step 5 :

There are three ways to create multithreading

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Correct ask

Put the above 3 Sort it out in two ways ：

1. Inherit Thread class
2. realization Runnable Interface
3. Anonymous classes

notes ： The starting thread is start() method ,run() Can't start a new thread

Step 6 :

practice - Find file contents synchronously

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Wrong posture , get half the results with double the effort ! Click to see the correct posture for the exercise

hold practice - Find the contents of the file Change to multithreading to find the contents of the file
The idea of the original exercise is to traverse all files , When traversing to the file is .java When I was , Find the contents of this file , After searching , Then traverse the next file

Now adjust this idea through multithreading ：
Traverse all files , When traversing to the file is .java When I was , Create a thread to find the contents of this file , You don't have to wait for this thread to end , Continue to traverse the next file

Step 7 :

answer - Find file contents synchronously

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This video is interpretive , So I hope you have read the content of this answer , Watch with questions , Only in this way can we gain more . It is not recommended to watch the video at the beginning

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First prepare a SerachFileThread, Inherit Thread class , And rewrite run method . stay run In the method , Read file contents and find

Then when traversing the file , If so .java ending , Then start a SerachFileThread Thread , Do the search

SearchFileThread.java
TestThread.java

More lines of code , Please click to view

package multiplethread;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class SearchFileThread extends Thread{

	private File file;
	private String search;
	public SearchFileThread(File file,String search) {
		this.file = file;
		this.search= search;
	}
	
	public void run(){
		String fileContent = readFileConent(file);
		if(fileContent.contains(search)){
		    System.out.printf(" Sub target string found %s, In the file :%s%n",search,file);
		}
	}
	
	public String readFileConent(File file){
        try (FileReader fr = new FileReader(file)) {
            char[] all = new char[(int) file.length()];
            fr.read(all);
            return new String(all);
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
 
    }	

}

More lines of code , Please click to view

package multiplethread;
 
import java.io.File;
 
public class TestThread {
 
    public static void search(File file, String search) {
        if (file.isFile()) {
            if(file.getName().toLowerCase().endsWith(".java")){
            	// When you find .java When you file , Just start a thread , Make a special search 
            	new SearchFileThread(file,search).start();
            }
        }
        if (file.isDirectory()) {
            File[] fs = file.listFiles();
            for (File f : fs) {
                search(f, search);
            }
        }
    }
     
    public static void main(String[] args) {
        File folder =new File("e:\\project");
        search(folder,"Magic");
    }
}

Multithreading series teaching materials （ two ）- Java Common threading methods

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Q & A area

2021-10-09 Multithreading to find file contents

wait4132

about JAVA Intermediate - Multithreading - Start a thread - answer - Find file contents synchronously Your questions

hold practice - Find the contents of the file Change to multithreading to find the contents of the file The idea of the original exercise is to traverse all files , When traversing to the file is .java When I was , Find the contents of this file , After searching , Then traverse the next file Now adjust this idea through multithreading ： Traverse all files , When traversing to the file is .txt When I was , Create a thread to find the contents of this file , You don't have to wait for this thread to end , Continue to traverse the next file

package Thread;
import java.io.File;
import java.io.FileReader;
import java.io.BufferedReader;
public class MultiThreading {
	// Multithreading to find file contents 
	
public static void main(String[] args) {
	File f=new File("E:\\how2j.com\\ Multithreading to find files ");
	Find.find(f);
}
}
class Check extends Thread
{
	String fn;
	public Check(String fn)
	{
		this.fn=fn;
	}
	public void run()
	{
		try
		{
			// Thread pause 
			Thread.sleep(1000);
		}
		catch(Exception e)
		{
			e.printStackTrace();
		}
		// The contents of the output file 
		File f=new File(fn);
		try(FileReader in=new FileReader(f);
				BufferedReader bin=new BufferedReader(in);)
		{
			
			StringBuffer s=new StringBuffer();
			String line;
			while((line=bin.readLine())!=null)
			{
				s.append(line+"\n");
				
			}
			System.out.println(s);
		}
		catch(Exception e)
		{
			e.printStackTrace();
		}
	}
}
class Find
{
	public static void find(File f)
	{
		if(!f.exists())return;
		File[] fs=f.listFiles();
		for(File f1:fs)
		{
			if(f1.isFile())
			{
			// If it is a file, judge whether the file suffix is .txt	
			String[] s1=f1.getName().split("\\.");
			// Not in the form of "." As a separation "." Is a special character that needs to be escaped 
			if(s1.length!=0&&s1[s1.length-1].equals("txt"))
				// To determine the equality of strings, you need to use equals out-of-service ==
			{
				// yes txt File words , Create the contents of the thread output 
				Check c=new Check(f1.getAbsolutePath());
				c.start();
			}
			}
			else if(f1.isDirectory())
				// If it's a folder, recursively traverse 
			{
				find(f1);
			}
		}
		
	}
}

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2021-08-22 It should be right , Interleaved different documents

Black vortex

about JAVA Intermediate - Multithreading - Start a thread Your questions

hold practice - Find the contents of the file Change to multithreading to find the contents of the file The idea of the original exercise is to traverse all files , When traversing to the file is .java When I was , Find the contents of this file , After searching , Then traverse the next file Now adjust this idea through multithreading ： Traverse all files , When traversing to the file is .java When I was , Create a thread to find the contents of this file , You don't have to wait for this thread to end , Continue to traverse the next file

public static void main(String[] args) {
        File file = new File("D:\\project\\tmall_ssm");
        String name = "a";
        one one = new one();
        one.search(file,name);
    }

    public void search(File file,String name){
//        System.out.println(" The file name is "+file);
        File[] files = file.listFiles();
        for (int i = 0;i < files.length;i++) {
            File f = files[i];
            if (files[i].getName().contains(name)) {
                System.out.printf(" The thread has found a file containing %s My files , file location %s\r\n", name, files[i].getAbsolutePath());
                if (files[i].isDirectory()) {
                    new Thread() {
                        @Override
                        public void run() {
                            System.out.println(" Thread created ");
                            search(f, name);
                        }
                    }.start();
                }
            } else {
                if (f.isDirectory()) {
                    search(f, name);
                }
            }
        }

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2021-08-01 practice - Find the contents of the file

Mono

about JAVA Intermediate - Multithreading - Start a thread Your questions

hold practice - Find the contents of the file Change to multithreading to find the contents of the file The idea of the original exercise is to traverse all files , When traversing to the file is .java When I was , Find the contents of this file , After searching , Then traverse the next file Now adjust this idea through multithreading ： Traverse all files , When traversing to the file is .java When I was , Create a thread to find the contents of this file , You don't have to wait for this thread to end , Continue to traverse the next file

//  Enable threads 
public class ThreadStream {
	public static void main(String[] args) {
		// Under the target directory 
		File f = new File("E:/project");
		String search = "Magic";
		search(f,search);
	}    
	
	public static void search(File f, String search) {
		String[] s = f.list();
		File[] fl = new File[s.length];
		keyFind[] keys = new keyFind[s.length];
		for (int i = 0; i < s.length; i++) {
			fl[i] = new File(f.getAbsoluteFile() + "/" + s[i]);
			if (fl[i].isFile() && String.valueOf(fl[i]).contains(".java")) {
				keys[i] = new keyFind(new KeySearch(fl[i],search));
				new Thread(keys[i]).start();
			}
			if (fl[i].isDirectory()) { 
				search(fl[i],search);
			}
		}
	}
}

// Runnable Interface 
public class keyFind implements Runnable{
	private KeySearch k;
	
	public keyFind(KeySearch k) {
		this.k = k;
	}
	
	@Override
	public void run() {
		// TODO  Automatically generated method stub 
		k.search(k.folder, k.search);
	}
}

//  Imitate battle class 
public class KeySearch {
	public File folder;
	public String search;
	
	public KeySearch(File folder, String search) {
		this.folder = folder;
		this.search = search;
	}
	
	public void search(File folder, String search) {
		try {
			//  Find pause ,1000 millisecond 
			Thread.sleep(1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}		
		String[] s0 = read(folder);
		for (int j = 0; j < s0.length; j++) {
			if(String.valueOf(s0[j]).contains(search)) 
				System.out.printf(" Sub target string found %s, In the file ：%s\r\n", search, String.valueOf

(folder));	
		}	
}

	public String[] read(File f){*}
}

1 One answer

Mono
Answer time ：2021-08-08

practice - Multithreaded interaction On the basis of the above exercises , Increase the blood return thread to 2 strip , Reduce blood thread to 5 strip , Run at the same time . Run for a while , Observe the errors that will occur , Analyze the cause of the error , And consider solutions

 Copy thread t1  They are named t1 t2
 Copy thread t2  They are named t3、t4、t5、t6、t7
 Execute , No running errors have been found yet ;

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2021-07-23 Why don't the stationmaster demonstrate that the five dogs fly together 、Tab Flicker

2021-03-25 Threads and for Cycle

NBYXS

about JAVA Intermediate - Multithreading - Start a thread Your questions

Why multithreading and for The cycle time is not much different ？

2 One answer

KuroTT
Answer time ：2021-07-19

Too many threads created , Low efficiency .

Code exceeds 5 that 's ok , Click to view

Ah, spring
Answer time ：2021-05-10

Because it takes time for multiple threads to start , If the amount of time calculation is small , Maybe the main thread completes the task . It is recommended to use thread pool to experience , Increase the amount of calculation , It is also recommended that the number of threads you open should not exceed the number of threads in your computer's core 1/2

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about JAVA Intermediate - Multithreading - Start a thread Your questions

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