Java Swing - 如何替换文本区域中的文本...

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class Main extends JFrame {

  public Main() {
    // Create a text area with some initial text
    JTextArea textarea = new JTextArea("Initial Text");

    int rows = 20;
    int cols = 30;
    textarea = new JTextArea("Initial Text", rows, cols);
    this.getContentPane().add(new JScrollPane(textarea));

  }

  public static void main(String[] args) {
    JFrame frame = new Main();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    frame.pack();
    frame.setVisible(true);
  }
}