How to create line breaks in content using labels.

In Java, you can use HTML tags to implement line breaks in a label. Here is an example code:

import javax.swing.JFrame;
import javax.swing.JLabel;
public class Main {
    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        JLabel label = new JLabel("第一行
第二行");
        frame.add(label);
        
        frame.setVisible(true);
    }
}

The above code creates a simple GUI window and adds a label with line breaks in the window. We used the HTML `
` tag to indicate line breaks, placing the text that needs to break between `
` and `
` tags.

When running the above code, a window with two lines of text will be displayed, with each line on a separate line.