自动保存--Balking模式

男娘i 2023-07-22 03:59 13阅读 0赞

1，什么是Balking？

类似放弃作用，即本身有个线程准备响应时，发现另外一个线程已经响应，故当前线程放弃响应。

2，代码举例：

自动保存和手动保存

文档类

import java.io.File;
    import java.io.FileWriter;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    
    import static java.lang.Thread.currentThread;
    
    /**
     * 文档，表示当前正在操作的文档
     */
    public class Document {
        //如果文档改变，changed会被设置为true
        private boolean changed = false;
    
        //需要保存的内容
        private List<String> contents = new ArrayList();
    
        private final FileWriter writer;
    
        //自动保存文档的线程
        private static AutoSaveThread autoSaveThread;
    
        //构造函数，传入文档的路径和名称
        private Document(String path,String name) throws IOException {
            this.writer = new FileWriter(new File(path,name));
        }
    
        //创建文档
        public static Document create(String path,String name) throws IOException {
            Document document = new Document(path,name);
            autoSaveThread = new AutoSaveThread(document);
            autoSaveThread.start();
            return document;
        }
    
        //编辑文档
        public void edit(String content){
            synchronized (this){
                this.contents.add(content);
                //文档改变
                this.changed = true;
            }
        }
    
        //文档关闭时，中断文档自动保存线程，然后关闭writer流
        public void close() throws Exception{
            autoSaveThread.interrupt();
            writer.close();
        }
    
        //保存文档
        public void save() throws IOException {
            synchronized (this){
                //没有改变，就不执行。balking
                if(!changed){
                    return;
                }
    
                System.out.println(currentThread() + "执行保存任务");
                //将内容写入
                for(String content:contents){
                    this.writer.write(content);
                    this.writer.write("\r\n");
                }
    
                this.writer.flush();
                this.changed = false;
                this.contents.clear();
            }
        }
    }

自动保存线程

import java.io.IOException;
    import java.util.concurrent.TimeUnit;
    
    public class AutoSaveThread extends Thread {
    
        private final Document document;
    
        public AutoSaveThread(Document document) {
            super("DocumentAutoSaveThread");
            this.document = document;
        }
    
        @Override
        public void run() {
            while (true){
                try{
                    document.save();
                    TimeUnit.SECONDS.sleep(1);
                } catch (IOException| InterruptedException e) {
                    e.printStackTrace();
                    break;
                }
            }
        }
    }

文档编辑线程

import java.util.Scanner;
    
    public class DocumentEditThread extends Thread {
        private final String path;
        private final String name;
    
        private final Scanner scanner = new Scanner(System.in);
    
        public DocumentEditThread(String path,String name){
            super("DocumentEditThread");
            this.path = path;
            this.name = name;
        }
    
        @Override
        public void run() {
            int time = 0;
    
            try{
                Document document = Document.create(path,name);
                while (true){
                    String text = scanner.next();
                    if("quit".equals(text)){
                        document.close();
                        break;
                    }
    
                    document.edit(text);
                    if(time == 5){
                        document.save();
                        time = 0;
                    }
    
                    time++;
                }
            }catch (Exception e){
                throw new RuntimeException(e);
            }
        }
    }

测试类

public class BalkingTest {
        public static void main(String[] args) {
            new DocumentEditThread("./","balking.txt").start();
        }
    }