java多线程之Balking模式介绍

 
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
 
public class Data {
 
    private final  String fileName;
    private String content;
    private boolean changed;
 
    public Data(String fileName, String content) {
        this.fileName = fileName;
        this.content = content;
    }
 
    // 修改数据内容
    public synchronized void change(String newContent){
        content = newContent;
        changed = true;
    }
 
    // 若数据内容修改过。则保存到文件中
    public synchronized void save() throws IOException {
        if (!changed){
            return;
        }
        doSave();
        changed = false;
 
    }
 
    // 将数据内容实际保存到文件中
    private void doSave() throws IOException {
        System.out.println(Thread.currentThread().getName() + " calls doSave,content= " + content);
        Writer writer = new FileWriter(fileName);
        writer.write(content);
        writer.close();
    }
}

import java.io.IOException;
 
public class SaverThread extends  Thread{
 
    private final Data data;
 
    public SaverThread(String fileName ,Data data) {
        super(fileName);
        this.data = data;
    }
 
    @Override
    public void run() {
        try {
            while (true) {
                data.save();   // 要求保存数据
                Thread.sleep(1000);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
 
    }
}

import java.util.Random;
 
public class ChangerThread extends  Thread{
 
    private  final Data data;
    private  final Random random = new Random();
 
    public ChangerThread(String name ,Data data) {
        super(name);
        this.data = data;
    }
 
    @Override
    public void run() {
        try {
            for (int i = 0; true; i++) {
                data.change("No." + i);   // 修改数据
                Thread.sleep(random.nextInt(1000));  // 执行其他操作 ，只是随机暂停一段时间
                data.save();   // 显式的保存
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

 
public class Main {
    public static void main(String[] args) {
        Data data =  new Data("data.txt","(empty)");
        new ChangerThread("ChangerThread",data).start();
        new SaverThread("SaverThread",data).start();
    }
}

 
public class Something {
    private boolean initialized =false;
    public synchronized void init(){
        if (initialized){
            return;
        }
        doInit();
        initialized = true;
    }
    
    private void doInit(){
        // 处理逻辑
    }
}