《图解java多线程设计模式》中的 Balking 模式

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ChangerThread：修改并保存数据内容的类

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;
    }

    public void run(){
        try {
            for (int i =  0;true;i++){
                data.change("no. " +i);
                Thread.sleep(random.nextInt(1000));
                data.save();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Data：表示可以修改并保存的数据的类

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;
        this.changed = true;
    }

    //修改数据的内容
    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;
    }

    //将数据内容保存到文件中
    private void doSave() throws IOException {
        System.out.println(Thread.currentThread().getName() + " calls do save,content " +content);
        Writer writer = new FileWriter(filename);
        writer.write(content);
        writer.close();
    }
}

Main

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

ServerThread：定期保存数据内容的类

public class ServerThread extends Thread{
    private final Data data;
    public ServerThread(String name,Data data){
        super(name);
        this.data = data;
    }
    public void run(){
        try {
            while (true){
                data.save();
                Thread.sleep(1000);
            }
        }catch (Exception e){

        }
    }
}