调试java ，无法提交断点 LineBreakpoint exam3_6.java : 38，原因是：类 exam3_6 中的行 38 上未提供可执行文件的位

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无法提交断点 LineBreakpoint exam3_6.java : 38，原因是：类 exam3_6 中的行 38 上未提供可执行文件的位置。
无效的 LineBreakpoint exam3_6.java : 38
调试器在无法编译的源代码处停止。
线程 main 停止于 exam3_6.java:40。
用户程序已完成
代码如下：
public class exam3_6 {    /**
     * @param args the command line arguments
     */
    private int year,month,day;
    exam3_6()
     {
         year=2000;
         month=1;
         day=1;
     }
      exam3_6(int a,int b,int c)
    {
        year=a;
        month=b;
        day=c;
      }
      exam3_6(exam3_6 d)
      {
          year=d.year;
          month=d.month;
          day=d.day;    
      }
      public void outDate()
      {
          System.out.print(year+"/"+month+"/"+day);
      }
      public exam3_6  tomorrow()
        {
          exam3_6 d=new exam3_6(this);
          d.day++;
          if(d.day>d.daysInMonth())
          {
              d.day=1;
              d.month++;
              if(d.month>12)
              {
                  d.month=1;
                  d.year++;
              }
              return d;
          }
      }
      public int daysInMonth()
      {
          switch(month)
          {
              case 1:case 3:case 5:case 7:case 8:case 10:case 12:
                  return 31;
              case 4:case 6:case 9:case 11:
                  return 30;
                  default:
                      if(year%4==0&&year%100!=0&&year%400==0)
                          return 29;
                      else
                          return 28;
          }
      }
    public static void main(String[] args) {
        // TODO code application logic here
        exam3_6 d1=new exam3_6();
        System.out.print("The current date is(year/month/day):");
        d1.outDate();
        System.out.println();
        System.out.print("The tomorrow date is(year/month/day):");
        d1.tomorrow().outDate();
        System.out.println();
        exam3_6 dd=new exam3_6(2004,1,8);
        System.out.print("The current date is(year/month/day):");
        dd.outDate();
        System.out.println();
         System.out.print("The tomorrow date is(year/month/day):");
         dd.tomorrow().outDate();
          System.out.println();
        
        
        
        
    }
}