java运行时出现Exception in thread "main" java.lang怎样更改

完整代码如下，不清楚问题出现在哪，请求指点！

package javashiyaner;
import java.util.Scanner;
public class Javashiyaner {   
    public static void main(String[] args) {   
  int year;    
 int month; 
    Scanner reader=new Scanner(System.in);     System.out.println("请输入年份:");   
  year=reader.nextInt();  
   System.out.println("请输入月份:");   
  month=reader.nextInt();    
 while(true){         if(month<1||month>12)             System.out.println("输入有误请重新输入：");         else break;     }      
  judge(year,month);    }   
 private static void judge(int year, int month) {        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.    }
    }
class judge{
public judge(int nian,int yue){      
  switch(yue){
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:System.out.println("该月有31天");break;
case 4:
case 6:
case 9:
case 11:System.out.println("该月有30天");break;  
      case 2:
if(nian%4==0&&nian%100!=0||nian%400==0)
System.out.println("该月有29天");
else System.out.println("该月有28天");}
}


}

package javashiyaner;

import java.util.Scanner;

public class Javashiyaner {
    public static void main(String[] args) {
        int year;
        int month;
        Scanner reader = new Scanner(System.in);
        System.out.println("请输入年份:");
        year = reader.nextInt();
        System.out.println("请输入月份:");
        month = reader.nextInt();
        while (true) {
            if (month < 1 || month > 12)
                System.out.println("输入有误请重新输入：");
            else
                break;
        }
        judge(year, month);
    }

    public static void judge(int nian, int yue) {
        switch (yue) {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            System.out.println("该月有31天");
            break;
        case 4:
        case 6:
        case 9:
        case 11:
            System.out.println("该月有30天");
            break;
        case 2:
            if (nian % 4 == 0 && nian % 100 != 0 || nian % 400 == 0)
                System.out.println("该月有29天");
            else
                System.out.println("该月有28天");
        }
    }

}

??不是你自己throw的异常么