Someone plz help... how to block inputs

[waklo99]

(beginner question) I have a problem on my java assignment ~ I need to block an input if the user types letters or numbers... someone plz help TT^TT

heres my code so far:

import java.io.*;


public class GradingSystem
{
    public void Input()throws IOException{
    BufferedReader userInput=new BufferedReader(new InputStreamReader(System.in));
   
    String subject=" ", familyname=" ", firstname=" ", idnumber=" ", subject1=" ";
    double prelim=0.0, midterm=0.0, finals=0.0;
   
   
    try{
    System.out.println("\n\nenter subject:");
    subject1 = userInput.readLine();
    }catch(IOException ioe){}
   
    try{
    System.out.println("enter ID number:");
    idnumber = userInput.readLine();
        if(idnumber==" ")
   
    }catch(NumberFormatException nfe){System.out.println(nfe);}
   
    
    System.out.println("enter first name:");
    firstname = userInput.readLine(); [B]//i need to block or make it an error if the user types numbers[/B]
   
    System.out.println("enter family name:");
    familyname = userInput.readLine(); [B]// need to block or make it an error if the user types numbers[/B]
   
   
    
    System.out.println("enter prelim grade:");
    prelim=Integer.parseInt(userInput.readLine()); [B]//need to block or make it an error if the user types letters[/B]
   
    System.out.println("enter midterm grade:");
    midterm=Integer.parseInt(userInput.readLine());
   
    System.out.println("enter finals grade:");
    finals=Integer.parseInt(userInput.readLine());
    }catch(NumberFormatException nfe){System.out.println(nfe);}
   
    prelim*=(.3);
    midterm*=(.3);
    finals*=(.4);
    finals+= prelim+midterm;
   
    System.out.println("\n"+"\n"+subject1+"\n"+idnumber+"\n"+"\n"+firstname+", "+familyname+"\n"+"\n"+"Grade"+"\n"+"Prelim Grade: "+prelim+"\n"+"Midterm  Grade: "+midterm+"\n"+"Finals Grade: "+finals);
   
   
    System.out.println("Subject Grade: "+finals);
   
    }
   
}

Moderator Edit: code tags added to improve code readability

[Fubarable]

Consider placing the parseInt line in a try/catch NumberFormatException block. As for the name input, I'm not sure you want to trap numbers. What if someone is named James Spencer, 3rd?

[waklo99]

thnx for the reply, it gave me an idea... xD btw can you give me an idea on what other things you can put on the "try/catch" to block other inputs.... (coz i dont have an idea on what its called or what to search on the internet)

[Fubarable]

Read up on exceptions: Lesson: Exceptions (The Java™ Tutorials > Essential Classes)

[waklo99]

thnx for the replies... xD