Java getActionCommand() メソッド

package delftstack;

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;

class DemoFrame extends JFrame implements ActionListener {
  private JButton J_Button1, J_Button2, J_Button3;

  DemoFrame() {
    setTitle("getActionCommand");
    setLayout(new FlowLayout());
    setButtons();
    setAction();
    setSize(700, 200);
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }

  private void setButtons() {
    J_Button1 = new JButton("JButton One");
    J_Button2 = new JButton("JButton Two");
    J_Button3 = new JButton("JButton Three");
    add(J_Button1);
    add(J_Button2);
    add(J_Button3);
  }

  private void setAction() {
    J_Button1.addActionListener(this);
    J_Button1.setActionCommand("J_Button1");
    J_Button2.addActionListener(this);
    J_Button2.setActionCommand("J_Button2");
    J_Button3.addActionListener(this);
    J_Button3.setActionCommand("J_Button3");
  }

  public void actionPerformed(ActionEvent event) {
    if (event.getActionCommand() == "J_Button1")
      JOptionPane.showMessageDialog(rootPane, "The JButton One is Pressed");
    else if (event.getActionCommand() == "J_Button2")
      JOptionPane.showMessageDialog(rootPane, "The JButton Two is Pressed");
    else if (event.getActionCommand() == "J_Button3")
      JOptionPane.showMessageDialog(rootPane, "The JButton Three is Pressed");
  }
}

public class Example {
  public static void main(String[] args) {
    DemoFrame Demo_Frame = new DemoFrame();
  }
}