你好，我有一个问题与我的组合框。在应用程序中，我使我的面板有一个组合框，有两个选择和一个按钮旁边的组合框继续选择组合框，但相反，如果语句运行，没有我不知道为什么。

组合框代码简单私有JComboBox main Choice=new JComboBox（）；

main Choice. addItem（""）等…

class mainPanelGoButtonListener implements ActionListener
{
    public void actionPerformed(ActionEvent ae) 
    {
        String choice = (String)mainChoice.getSelectedItem();

        System.out.printf(choice);

        if(choice == "View Passenger Details");
        {
            JTextField first = new JTextField();
            JTextField last = new JTextField();

            Object[] message = {  
                    "First Name:", first,  
                    "Last Name:", last
            };  

            int option = JOptionPane.showConfirmDialog(null, message, "Enter passenger name", JOptionPane.PLAIN_MESSAGE);

            if (option == JOptionPane.OK_OPTION)  
            {  
                // Load passenger data
                p = dataHandler.getPassengerData(first.getText(), last.getText());
                if(p != null)
                {
                    updateTextfields( p);
                    // Display passenger data
                    getContentPane().removeAll();
                    getContentPane().add(passengerDetailsPanel);
                    setSize(400,340);
                    setLocationRelativeTo(null);
                    validate();
                    repaint();
                    printAll(getGraphics());
                }
            }
        }

        if(choice == "Add New Passenger")
        {
            if(displayPassengerInputForm());
            {
                // Display passenger data
                getContentPane().removeAll();
                getContentPane().add(passengerDetailsPanel);
                setSize(400,340);
                setLocationRelativeTo(null);
                validate();
                repaint();
                printAll(getGraphics());
            }
        }

    }
}

//返回窗口A和窗口B的程序示例

import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class Frame extends JFrame
{
private JPanel mainPanel = new JPanel();
private JComboBox<String> mainChoice = new JComboBox<String>();
private JButton goButton = new JButton("GO");

public Frame()
{
    createMainPanel();
    this.add(mainPanel);
}


private void createMainPanel()
{
    // Fill choice box
    mainChoice.addItem("Find Passenger");
    mainChoice.addItem("Add New Passenger");

    // Set button

    goButton.addActionListener(new mainPanelGoButtonListener());
    goButton.setPreferredSize(new Dimension(5,5));

    // Add to main panel
    mainPanel.setLayout(new GridLayout(1,2,4,4));
    mainPanel.add(mainChoice);
    mainPanel.add(goButton);

}


class mainPanelGoButtonListener implements ActionListener
{
    public void actionPerformed(ActionEvent ae) 
    {       
        if(mainChoice.getSelectedItem().equals("Find Passenger"));
        {
            // DISPLAYS WINDOW FOR INPUT
            System.out.printf(" WINDOW A ");

        }

        if(mainChoice.getSelectedItem().equals("Add New Passenger"));
        {
            // DISPLAYS WINDOW FOR INPUT
            System.out.printf(" WINDOW B ");
        }
    }
}

public static void main(String args[])
{
    Frame frame = new Frame();
    frame.setTitle("SSD Project");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
    frame.setSize(400,50);
    frame.setVisible(true);
}

}

每次我按下一个按钮，它都会同时打印出窗口A和窗口B，而不是一个