本人编了一个判断是否为闰年的小程序，出现了一些问题：
import javax.swing.JOptionPane;
public class year
{
    public static void main(String agrs[])
   {
     String nian;
     String result1;
     String result2;
     int n;
     result1="yes";
     result2="no";
     nian=JOptionPane.showlnputDialog("input the year");
     n=lnteger.parselnt(nian);
     if(n%4==0&&n%100!=0||n%400==0)
        JoptionPane.showMessageDialog(null,"The result is "+result1,"answer",JOptionPane.PLAN_MESSAGE);
     else
        JoptionPane.showMessageDialog(null,"The result is "+result2,"answer",JOptionPane.PLAN_MESSAGE);
   System.exit(0);  
}
}
结果如下：
D:\>javac year.java
year.java:12: 找不到符号
符号： 方法 showlnputDialog(java.lang.String)
位置： 类 javax.swing.JOptionPane
     nian=JOptionPane.showlnputDialog("input the year");
                     ^
year.java:13: 找不到符号
符号： 变量 lnteger
位置： 类 year
     n=lnteger.parselnt(nian);
       ^
year.java:15: 找不到符号
符号： 变量 PLAN_MESSAGE
位置： 类 javax.swing.JOptionPane
        JoptionPane.showMessageDialog(null,"The result is "+result1,"answer",JOp
tionPane.PLAN_MESSAGE);

        ^
year.java:15: 找不到符号
符号： 变量 JoptionPane
位置： 类 year
        JoptionPane.showMessageDialog(null,"The result is "+result1,"answer",JOp
tionPane.PLAN_MESSAGE);
        ^
year.java:17: 找不到符号
符号： 变量 PLAN_MESSAGE
位置： 类 javax.swing.JOptionPane
        JoptionPane.showMessageDialog(null,"The result is "+result2,"answer",JOp
tionPane.PLAN_MESSAGE);

        ^
year.java:17: 找不到符号
符号： 变量 JoptionPane
位置： 类 year
        JoptionPane.showMessageDialog(null,"The result is "+result2,"answer",JOp
tionPane.PLAN_MESSAGE);
        ^
6 错误

经过我自己的改正，终于把所有的问题找到了，主要问题是把小写“l”于大写“i”弄混乱了，不过还是谢谢你！！！另外也提醒初学者要看清书本。下面是我改正后的代码（判断是否是闰年）：
import javax.swing.JOptionPane;
public class year
{
    public static void main(String agrs[])
   {
     String nian;
     String result1;
     String result2;
     int n;
     int i;
     result1="yes";
     result2="no";
     nian=JOptionPane.showInputDialog("input the year");
     for(i=0;i<nian.length();i++)
     {
      n=nian.charAt(i);
      if(n>='0'&&n<='9') continue;
      else
        {
         JOptionPane.showMessageDialog(null,"Your input is error!!!");
         System.exit(0);
         }
      }
     n=Integer.parseInt(nian);
     if(n%4==0&&n%100!=0||n%400==0)
        JOptionPane.showMessageDialog(null,"The result is "+result1,"answer",JOptionPane.PLAIN_MESSAGE);
     else
        JOptionPane.showMessageDialog(null,"The result is "+result2,"answer",JOptionPane.PLAIN_MESSAGE);
   System.exit(0);  
}
}