[在Java中，如何在TextArea中使用多线程？我需要同步我的线程吗？

Question

我对Java和多线程没有经验，所以也许你们可以帮忙。多线程时，在TextArea框中打印一系列数字和字母时遇到问题。这是我的代码：

public class MultiThread extends Application {
    static TextArea outputArea = new TextArea();
@Override
    public void start(Stage primaryStage) throws Exception {

        outputArea.setWrapText(true);
        Runnable printA = new PrintChar('a', 100);
        Runnable printB = new PrintChar('b', 100);
        Runnable print100 = new PrintNum(100);

        // Create threads
        Thread thread1 = new Thread(printA);
        Thread thread2 = new Thread(printB);
        Thread thread3 = new Thread(print100);

        thread1.start();
        thread2.start();
        thread3.start();

        Scene scene = new Scene(outputArea, 250, 130);
        primaryStage.setTitle("Concurrent Output");
        primaryStage.setScene(scene);
        primaryStage.show();}


    public static void main(String[] args) {
        launch(args);
    }
}
class PrintChar extends MultiThread implements Runnable {
    private char charToPrint; // The character to print
    private int times; // The times to repeat

    public PrintChar(char c, int t) {
        charToPrint = c;
        times = t;
    }

    @Override
    public void run() {
        for (int i = 0; i < times; i++) {
            outputArea.appendText(charToPrint + "");
        }
    }
}

class PrintNum extends MultiThread implements Runnable {
    private int lastNum;
    private char charToPrint;

    public PrintNum(int n) {
        lastNum = n;
    }

    @Override
    public void run() {
        for (int i = 1; i <= lastNum; i++) {
            outputArea.appendText(i + "");
        }
    }
}

当我运行代码时，线程通常不会打印出它们应有的全部内容。例如，“ print100”并不总是像预期的那样打印到100号。我也会得到随机结果，而每次都不会得到相同的输出也不会出错。

Exception in thread "Thread-6" Exception in thread "Thread-4" java.lang.IndexOutOfBoundsException
    at javafx.scene.control.TextInputControl.getText(TextInputControl.java:451)
    at javafx.scene.control.TextInputControl.updateContent(TextInputControl.java:564)
    at javafx.scene.control.TextInputControl.replaceText(TextInputControl.java:548)
    at javafx.scene.control.TextInputControl.insertText(TextInputControl.java:473)
    at javafx.scene.control.TextInputControl.appendText(TextInputControl.java:463)
    at threader.PrintChar.run(Threader.java:53)
    at java.lang.Thread.run(Thread.java:748)
java.lang.IndexOutOfBoundsException
    at javafx.scene.control.TextInputControl.getText(TextInputControl.java:451)
    at javafx.scene.control.TextInputControl.updateContent(TextInputControl.java:555)
    at javafx.scene.control.TextInputControl.replaceText(TextInputControl.java:548)
    at javafx.scene.control.TextInputControl.insertText(TextInputControl.java:473)
    at javafx.scene.control.TextInputControl.appendText(TextInputControl.java:463)
    at threader.PrintNum.run(Threader.java:71)
    at java.lang.Thread.run(Thread.java:748)

我几乎可以肯定的是，同步代码中的多个线程是一个问题，但是我似乎无法弄清楚该特定代码的处理方法。

Answer 1

TextArea实现显然不是线程安全的，因此在调用TextArea对象上的方法时，应确保当前线程没有中断。例如，您可以通过同步TextArea对象本身来执行此操作：

synchronized (outputArea) {
    outputArea.appendText(charToPrint + "");
}