Programming Forums > Application Development > Java

BungalowBill · May 3rd, 2007, 7:31 AM

I've got two methods which take in information from the user. One which takes in Strings:

public static String getNames(){
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        
        String name = null;
        
        try{
            name = br.readLine();         
        } catch (IOException ioe){
            System.out.println("Error trying to read input");
            System.exit(1);
        }
        
        return name;
    }

and one which takes in Integers:

(Toggle Plain Text)

public int getNums()
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        
        String input = null;
        int num = 0;
        
        try{
           input = br.readLine();
           num = Integer.parseInt( input );
        } catch (IOException ioe){
            System.out.println("Error trying to read input");
            System.exit(1);
        }
        
        return num;
    }

The problem is that if the user enters a string when the system expects an integer, there is an error and the system crashes.

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "r"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)

Any idea on what to write to ensure the user enters an integer when asked?

kruptof · May 3rd, 2007, 8:00 AM

"Please enter a number from [min] to [max]....if you don't enter a number this program will crash"

DaWei · May 3rd, 2007, 9:20 AM

While that seems like a joke, there is a large measure of truth involved. YOU DO NOT HAVE CONTROL OF YOUR USER. Instead, you use a function that tells you whether or not the user complied with your requirements. Then you check what the function had to say. If your function doesn't have that ability, the function was written by a schlock. If your function has that ability, but you don't use it, you are either uninformed, or a schlock.

ReggaetonKing · May 3rd, 2007, 9:33 AM

Just have another catch statement to catch the NumberFormatException!

(Toggle Plain Text)

public int getNums()
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        
        String input = null;
        int num = 0;
        
        try
        {
           input = br.readLine();
           num = Integer.parseInt( input );
        } 
        catch (IOException ioe)
        {
            System.out.println("Error trying to read input");
            System.exit(1);
        } 
        catch(NumberFormatException nfe)
        {
           System.out.println("enter an integer value!!");
           System.out(1);
        }
        
        return num;
    }

May 3rd, 2007, 7:31 AM	#1
BungalowBill Programmer Join Date: Dec 2005 Posts: 40 Rep Power: 0	Little Error checking help I've got two methods which take in information from the user. One which takes in Strings: (Toggle Plain Text) public static String getNames(){ BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String name = null; try{ name = br.readLine(); } catch (IOException ioe){ System.out.println("Error trying to read input"); System.exit(1); } return name; } public static String getNames(){ BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String name = null; try{ name = br.readLine(); } catch (IOException ioe){ System.out.println("Error trying to read input"); System.exit(1); } return name; } and one which takes in Integers: (Toggle Plain Text) public int getNums() { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String input = null; int num = 0; try{ input = br.readLine(); num = Integer.parseInt( input ); } catch (IOException ioe){ System.out.println("Error trying to read input"); System.exit(1); } return num; } public int getNums() { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String input = null; int num = 0; try{ input = br.readLine(); num = Integer.parseInt( input ); } catch (IOException ioe){ System.out.println("Error trying to read input"); System.exit(1); } return num; } The problem is that if the user enters a string when the system expects an integer, there is an error and the system crashes. Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "r" at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48) Any idea on what to write to ensure the user enters an integer when asked?

May 3rd, 2007, 9:20 AM	#3
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	While that seems like a joke, there is a large measure of truth involved. YOU DO NOT HAVE CONTROL OF YOUR USER. Instead, you use a function that tells you whether or not the user complied with your requirements. Then you check what the function had to say. If your function doesn't have that ability, the function was written by a schlock. If your function has that ability, but you don't use it, you are either uninformed, or a schlock. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

May 3rd, 2007, 9:33 AM	#4
ReggaetonKing Sexy Programmer Join Date: Nov 2005 Location: New Jersey Posts: 891 Rep Power: 3	Just have another catch statement to catch the NumberFormatException! (Toggle Plain Text) public int getNums() { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String input = null; int num = 0; try { input = br.readLine(); num = Integer.parseInt( input ); } catch (IOException ioe) { System.out.println("Error trying to read input"); System.exit(1); } catch(NumberFormatException nfe) { System.out.println("enter an integer value!!"); System.out(1); } return num; } public int getNums() { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String input = null; int num = 0; try { input = br.readLine(); num = Integer.parseInt( input ); } catch (IOException ioe) { System.out.println("Error trying to read input"); System.exit(1); } catch(NumberFormatException nfe) { System.out.println("enter an integer value!!"); System.out(1); } return num; } __________________ I would love to change the world, but they won't give me the source code!

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Programming Forums > Application Development > Java

Little Error checking help