java窗体确定键出现内容

这个点确定键怎么出现内容，
只能做到这
import java.awt.;
import java.awt.event.;

import javax.swing.*;

public class day extends JFrame implements ActionListener,ItemListener{

public day() {
    initComponents();
}
private void initComponents() {

    birth = new javax.swing.JLabel();
    box1 = new javax.swing.JComboBox();
    year = new javax.swing.JLabel();
    box2 = new javax.swing.JComboBox();
    mouth = new javax.swing.JLabel();
    box3 = new javax.swing.JComboBox();
    day = new javax.swing.JLabel();
    button1 = new javax.swing.JButton();
    button2 = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    getContentPane().setLayout(new java.awt.FlowLayout());

    birth.setText("\u51fa\u751f\u65e5\u671f\uff1a");
    getContentPane().add(birth);

    box1.setModel(new javax.swing.DefaultComboBoxModel(new String[] {
            "1990", "1991", "1992", "1993", "1994", "1995", "1996", "1997",
            "1998", "1999", "2000" }));
    getContentPane().add(box1);

    year.setText("\u5e74");
    getContentPane().add(year);
    

    box2.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "1",
            "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12" }));
    getContentPane().add(box2);
    box2.addItemListener(this);

    mouth.setText("\u6708");
    
    getContentPane().add(mouth);

    box3.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "1",
            "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13",
            "14", "15", "16", "17", "18", "19", "20", "21", "22", "23",
            "24", "25", "26", "27", "28", "29", "30" ,"31"}));
    getContentPane().add(box3);

    day.setText("\u65e5");
    getContentPane().add(day);

    button1.setText("\u786e\u5b9a");
    button1.addActionListener(this);
    getContentPane().add(button1);

    button2.setText("\u53d6\u6d88");
    getContentPane().add(button2);
    this.setTitle("出生日期");
    this.setLocation(200, 200);
    this.setPreferredSize(new Dimension(350,130));
    
    pack();
}
public static void main(String args[]) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new day().setVisible(true);
        }
    });
}
private javax.swing.JLabel birth;
private javax.swing.JComboBox box1;
private javax.swing.JComboBox box2;
private javax.swing.JComboBox box3;
private javax.swing.JButton button1;
private javax.swing.JButton button2;
private javax.swing.JLabel day;
private javax.swing.JLabel mouth;
private javax.swing.JLabel year;

public void itemStateChanged(ItemEvent e) {
    int a,b;
    a=Integer.parseInt((String)box2.getSelectedItem());
    b=Integer.parseInt(box1.getSelectedItem().toString());
    switch (a) {
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
    case 12: 
        box3.removeAllItems();
        for(int i=1;i<=31;i++)
            box3.addItem(i);
        break;
    case 4:
    case 6:
    case 9:
    case 11:
        box3.removeAllItems();
        for(int i=1;i<=30;i++)
            box3.addItem(i);
        break;
  case 2:
    if(b%4==0 && b%100!=0 || b%400==0){
        box3.removeAllItems();
        for(int i=1;i<30;i++)
            box3.addItem(i);
    }else {
        box3.removeAllItems();
        for(int i=1;i<29;i++)
            box3.addItem(i);
    
        
    }
    }
  
    
    }
@Override
public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    
}

}

不知道你要出现什么内容，我先打印了一下时间选择结果，你参考实现一下吧，具体做法就是你没写内容的actionPerformed方法内加具体实现就行

public void actionPerformed(ActionEvent e) {
        if(e.getActionCommand().equals("确定")){
            System.out.println(this.box1.getSelectedItem());
            System.out.println(this.box2.getSelectedItem());
            System.out.println(this.box3.getSelectedItem());
        }
    }