请各位前辈帮我看一下我的这个程序，能够编译，但是运行结果有错，麻烦帮我改一下，谢谢！

/*
  输入年月日，判断多少岁
 */
 import javax.swing.*;
 import java.text.*;
 import java.util.*;
 class xxx
 {
 
  public static void main(String [] args)
  {
      String aaa,bbb,ccc; 
      int  a,year,mon,day,age,nyear,nmon,nday,nage,xage;
      Date today = new Date();
         GregorianCalendar cal = new GregorianCalendar();
         nyear = cal.get(Calendar.YEAR);
         nmon = cal.get(Calendar.MONTH);
         nday = cal.get(Calendar.DATE);
           aaa = JOptionPane.showInputDialog(null,"请输入你的生日的年份:");
       year = Integer.parseInt(aaa);
             bbb = JOptionPane.showInputDialog(null,"请输入你的生日月份:");
             mon  =Integer.parseInt(bbb);
           
            ccc = JOptionPane.showInputDialog(null,"请输入你的生日日期:");
               day = Integer.parseInt(ccc);
            
              if(nyear>year||nmon>=mon)
              {
               age = nyear-year;
            JOptionPane.showMessageDialog(null,"你的出生是:"+
                               year+"年"+mon+"月"+day+"日"+"\n"        
                                              +"你今年是:" + age+"岁");
              }
              else if(nyear>year||nmon>=mon||nday<=day)
              {
               nage = nyear-year-1;
               JOptionPane.showMessageDialog(null,"你的出生是:"+
                              year+"年"+mon+"月"+day+"日"+"\n"        
                                              +"你今年是:" + nage+"岁");
              }
              else
            {
                xage = nyear-year-1;
               JOptionPane.showMessageDialog(null,"你的出生是:"+
                               year+"年"+mon+"月"+day+"日"+"\n"        
                                              +"你今年是:" + xage+"岁");
              }
  } 
 }