HashTable In Java

Here is a Hash Table program in java.

In this program we are going to,

 1]Accept n  records of student(Name,percentage)
 2]Disply details of all students
 3]Find out highest marks

 import java.util.*;
 import java.io.*;
 class Slip1_2
 {
   public static void main(String args[]) throws IOException
   {
     
       Slip1_2 htc = new Slip1_2();
       BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int opt=1;
      while(opt!=4)
       {
         
           System.out.println("1:Enter Record");
           System.out.println("2:Disply Details");
           System.out.println("3:Find Highest Marks");
           System.out.println("4:Exit");
           System.out.print("Select Option : ");
      
        int r=Integer.parseInt(br.readLine());
      
        System.out.println();
        
           switch(r)
           {
               case 1:htc.get_record();      break;
               case 2:htc.disp_record();    break;
               case 3:htc.highest_record(); break;
               case 4:System.exit(0);
           }//switch
       }//while
     }//main


     Hashtable ht =new Hashtable();
     //Enumeration names;
     String nm;
    Slip1_2(){ }
    void get_record() throws IOException
     {
       BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
       System.out.print("Enter n Records of stud : ");       int n=Integer.parseInt(br.readLine());
       Double d;
          System.out.println();
          for(int i=0;i<n;i++)
          {
               System.out.print("Enter Name : ");    nm = br.readLine();
              System.out.print("Enter Percentage : ");   d = Double.parseDouble(br.readLine());
              System.out.println();
              ht.put(nm,d);
          }
      }
    
         
   
   
     void disp_record()
     {
         Enumeration names= ht.keys();
         //Returns an enumeration of the keys in this hashtable. <-=keys()
         while(names.hasMoreElements())     //Tests if this enumeration contains more elements.
         {
             nm=(String)names.nextElement();
                             //the next element of this enumeration.
 
              System.out.print(nm+" => "+ht.get(nm));
              //Returns the value to which the specified key is mapped in this hashtable.
              System.out.println();
         }
             System.out.println();
      }
  
     void highest_record()
     {
         Collection c=ht.values();
         //Object obj=Collections.max(c);
         //System.out.println("Highest Marks: "+obj);
         System.out.println("Highest Marks: "+Collections.max(c));
     }   
   
 }