Javaswing显示年月日

import java.awt.Dimension;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

import javax.swing.JFrame;

public class r1 extends JFrame implements ItemListener{

/** Creates new form r1 */
public r1() {
    initComponents();
}

private void initComponents() {

    jLabel4 = new javax.swing.JLabel();
    y = new javax.swing.JComboBox();
    jLabel1 = new javax.swing.JLabel();
    m = new javax.swing.JComboBox();
    jLabel2 = new javax.swing.JLabel();
    d = new javax.swing.JComboBox();
    jLabel3 = new javax.swing.JLabel();

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

    jLabel4.setText("\u51fa\u751f\u65e5\u671f:");
    getContentPane().add(jLabel4);
    for(int i=1980;i<2022;i++){
        y.addItem(i);
    }
    getContentPane().add(y);

    jLabel1.setText("\u5e74");
    getContentPane().add(jLabel1);

    for(int i=1;i<13;i++){
        m.addItem(i);
    }
    getContentPane().add(m);

    jLabel2.setText("\u6708");
    getContentPane().add(jLabel2);

    for(int i=1;i<32;i++){
        d.addItem(i);
    }
    getContentPane().add(d);
    
    jLabel3.setText("\u65e5");
    getContentPane().add(jLabel3);
    m.addItemListener(this);
    y.addItemListener(this);
    this.setTitle("出生日期");
    this.setLocation(200,200);
    this.setPreferredSize(new Dimension(400,180));
    pack();
}// </editor-fold>
//GEN-END:initComponents

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new r1().setVisible(true);
        }
    });
}

//GEN-BEGIN:variables
// Variables declaration - do not modify
private javax.swing.JComboBox d;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JComboBox m;
private javax.swing.JComboBox y;

public void itemStateChanged(ItemEvent e) {
    int mm=0,mmm=30,yy=0;
    mm=Integer.parseInt(m.getSelectedItem().toString());
    yy=Integer.parseInt(y.getSelectedItem().toString());
    switch(mm){
    case 4:
    case 6:
    case 9:
    case 11:
        d.remove(mmm);
        break;
    case 2:
        if(yy%4==0 && yy%100!=0 || yy%400==0){
            d.remove(mmm);
            d.remove(mmm-1);
            }else{
                d.remove(mmm);
                d.remove(mmm-1);
                d.remove(mmm-2);
            }
    }
}

}
运行选择月份时，报错，数组下标越界，求解

这是最终效果图