Java，剪贴板代码不起作用，

Question

程序应该分析剪贴板中存在的5位数字，从1开始。问题是，在复制文本时，我不回答if (clipboardContent.length () == 5)程序停止工作。

import java.awt.*;
import java.awt.datatransfer.*;
import java.io.IOException;

public class drob implements FlavorListener {
    private static Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();

    public static void main(String[] args) throws InterruptedException {
        clipboard.addFlavorListener(new drob());

 //  fall asleep for 100 seconds, otherwise the program will immediately end

        Thread.sleep(100 * 1000);
    }

    @Override
    public void flavorsChanged(FlavorEvent event) {
        try {
            String clipboardContent = (String) clipboard.getData(DataFlavor.stringFlavor);
            handleClipboardContent(clipboardContent);
        } catch (UnsupportedFlavorException | IOException e) {
            // TODO handle the error

            e.printStackTrace();
        }
    }

    private void handleClipboardContent(String clipboardContent) {
        // check if the string satisfies condition
           

 // for example, check that the length of the string is five

        if (clipboardContent.length() == 5) {
            System.out.println(clipboardContent);

        }
    }
}

Answer 1

您没有检查clipboardContent null。只需改变：

if (clipboardContent.length() == 5) {...}

为：

if (clipboardContent != null && clipboardContent.length() == 5) {...}