使用显示器的Writer / Reader不工作(Writer/Reader using Monitor not working)

 我正在做一个任务，在哪里实现一个使用监视器进行同步的Writer / Reader问题。 
 
 场景：作者应该从列表中一次一个地写入一个字符串到缓冲区中（缓冲区一次只能保存一个字符串）。 然后阅读器应该从缓冲区中读取字符串，并在打印之间暂停0.5秒后在gui中打印字符串。 该程序使用一个单独的编写器线程和一个单独的读取器线程，当gui中的一个按钮被按下时，这些线程同时启动。 
 
 我的问题是：我无法使同步工作，读者只需每0.5秒输出一个空值（这意味着当阅读器试图从中读取时缓冲区很可能是空的）。 我设法发现一个错误：作家没有达到try buffer.put(text.get(i)) ，尽管我找不出原因。 
 
 任何人可以帮助？ 非常感激！ 我的代码在下面，希望它够了，我不想垃圾太多的代码。 （我也很喜欢Writer / Reader问题，但已经阅读了一些编码示例等） 
 
 作家： 
 
public void run() {
    buffer.length(text.size());
    for (int i = 0; i < text.size(); i++) { //loops thorugh the list of strings
        System.out.println("hj"); //reaches this
        try {
            buffer.put(text.get(i)); //put the string into the buffer
            System.out.println("put done"); // never reaches this
            sleep(); //pauses the thread for 0.5 seconds
        } catch (InterruptedException e) {
            System.out.println("error"); //never reaches this either
            e.printStackTrace();
        }
    }
}
 
 缓冲： 
 
/**
 * gets a string from the writer
 * @throws InterruptedException 
 */
public synchronized void put(String string) throws InterruptedException {
    while(hasString == false) { //we only want to put a string into the buffer if it is empty
        wait();
        this.string = string;
        hasString = true;
        notify();
    }
}

/**
 * passes on a string to the reader
 * @throws InterruptedException 
 */
public synchronized String get() throws InterruptedException {
    while(hasString == true) { //we only want to pass on a string if the buffer is NOT empty
        wait();
        hasString = false;
        notify();
    }
    return string;
}
 
 读者： 
 
/**
 * reads a string from the buffer and writes it to the gui in the destination-tab
 */
public void run() {
    for (int i  = 0; i < buffer.getLength(); i++) { //loops through the length of the list with strings
        try {
            string = buffer.get(); //gets string from buffer
        } catch (InterruptedException e1) {
            e1.printStackTrace();
        }
        //writes the string in the gui
        sb.append(string);
        GUIMonitor.txtPaneDest.setText(sb.toString());
        try {
            sleep(); //pauses the thread for 0.5 seconds
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

I´m doing an assignment where are implementing a Writer/Reader problem that uses a monitor for synchronization. 
 
The scenario: The writer should write a string from a list one at a time into a buffer (the buffer can only hold one single string at a time). The reader should then read the string from the buffer and print the string in a gui with a 0.5 second pause between the prints. The program uses one singular writer-thread and one singular reader-thread, which are started simultaneously when a button in the gui is pressed.
 
My problem: I cannot get the synchronization to work, the reader just prints out null every 0.5 seconds (which means the buffer is most likely empty when the reader tries to read from it). I managed to find an error: the writer is not reaching the try where buffer.put(text.get(i)), though I cannot figure out why. 
 
Anyone who could help?? Much appreciated! My code is down below, hope it is enough, I don´t want to spam too much code. (I´m also pretty new with the Writer/Reader problem but have read some coding examples etc.)
 
Writer: 
 
public void run() {
    buffer.length(text.size());
    for (int i = 0; i < text.size(); i++) { //loops thorugh the list of strings
        System.out.println("hj"); //reaches this
        try {
            buffer.put(text.get(i)); //put the string into the buffer
            System.out.println("put done"); // never reaches this
            sleep(); //pauses the thread for 0.5 seconds
        } catch (InterruptedException e) {
            System.out.println("error"); //never reaches this either
            e.printStackTrace();
        }
    }
}
 
Buffer:
 
/**
 * gets a string from the writer
 * @throws InterruptedException 
 */
public synchronized void put(String string) throws InterruptedException {
    while(hasString == false) { //we only want to put a string into the buffer if it is empty
        wait();
        this.string = string;
        hasString = true;
        notify();
    }
}

/**
 * passes on a string to the reader
 * @throws InterruptedException 
 */
public synchronized String get() throws InterruptedException {
    while(hasString == true) { //we only want to pass on a string if the buffer is NOT empty
        wait();
        hasString = false;
        notify();
    }
    return string;
}
 
Reader:
 
/**
 * reads a string from the buffer and writes it to the gui in the destination-tab
 */
public void run() {
    for (int i  = 0; i < buffer.getLength(); i++) { //loops through the length of the list with strings
        try {
            string = buffer.get(); //gets string from buffer
        } catch (InterruptedException e1) {
            e1.printStackTrace();
        }
        //writes the string in the gui
        sb.append(string);
        GUIMonitor.txtPaneDest.setText(sb.toString());
        try {
            sleep(); //pauses the thread for 0.5 seconds
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

原文：https://stackoverflow.com/questions/47968345