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Thread: java.lang.numberformatexception error

  1. #1
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    Default java.lang.numberformatexception error

    Hi, im new to java, and im having a problem.
    i have written a program that allows the user to select a choice 1-5 from a menu. then the desired info is displayed. if any other numbers are entered and error message appears. but i would like this error message to appear also if the user enters a symbol or anything that is not a number 1-5. how do i do this?

    whenever i enter a symbol i get a java.lang.numberformatexception error message.i know it has to do with the highlighted area.

    below is part of my code:

    do
    		{
    			do
    			{
    				//Runs Public Static void display_menu()
    				display_menu();
    				[COLOR="Red"]choice = Integer.valueOf(in.readLine()).intValue();[/COLOR]
     
    				if ((choice < 1) || (choice > 5))
    				{
    					System.out.println("Error: invalid choice, please try again");
    				}
    			} while ((choice < 1) || (choice > 5));
    			if (choice != 5)
    			{
    				switch (choice)
    				{
    					case 1: 
    						//Runs Public Static void Village()
    						village();
    						break;
    					case 2:
    						//Creates Output Text
    						System.out.println("----------------------------");
    						System.out.println("---Milk Round Information---");
    						System.out.println("----------------------------");
    						System.out.println("Distributer's Name: Ben Siddall");
    						System.out.println("Number of Pints Needed for Sale each day: " + milkman.pints_to_be_available_daily());
    						System.out.println("Total Revenue for the Milk Round each week: "  + myFormat.format(milkman.milk_round_revenue())+" Pounds");
    						break;
    					case 3:
    						//Creates Output ~Text
    						System.out.println("-------------------------");
    						System.out.println("---Farmer Information---");
    						System.out.println("-------------------------");
    						System.out.println("Farmer's Name: Caleb Green");
    						System.out.println("Number of Pints needed each day: " + milkman.pints_to_be_available_daily());
    						System.out.println("Number of Cows required to Produce milk: " + farmer.cows_required(milkman.pints_to_be_available_daily()));
    						System.out.println("Total Revenue for the Farmer each week: " + myFormat.format(milkman.farmers_revenue()) +" Pounds");
    						System.out.println("Predicted Annual Milk Production: " + farmer.expected_pints_year() + " Pints");
     
    						break;
    					case 4:
    						//creates output text
    						System.out.println("-------------------------");
    						System.out.println("---Revenue Information---");
    						System.out.println("-------------------------");
    						System.out.println("Milk Round Revenue: " + myFormat.format(milkman.milk_round_revenue()) + " Pounds");
    						System.out.println("Farmers Revenue: " + myFormat.format(milkman.farmers_revenue()) + " Pounds");
    						System.out.println("Farmers percentage of the milk round revenue: " +  myFormat.format(milkman.farmers_percentage_revenue()) + " % ");
    						System.out.println("Predicted Annual Revenue for the Milk Round: " + myFormat.format(milkman.annual_milk_revenue())  + " Pounds");
     
    						break;
    					default:
    						break;
    				}
    			}
    		} while (choice != 5);
    Last edited by Json; February 18th, 2010 at 09:33 AM. Reason: Please use code tags.


  2. #2
    Super Moderator Json's Avatar
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    Default Re: java.lang.numberformatexception error

    Hello,

    The problem you have is that the input you receive in in.readLine() is not a number and when that happens the JVM throws a NumberFormatException.

    There is also a somewhat shorter way for you to get the integer value from the string as a primitive.

    choice = Integer.parseInt(in.readLine());

    To solve your problem and print an error you can do this.

    try {
        choice = Integer.parseInt(in.readLine());
    } catch (Throwable throwable) {
        System.out.println("Error: your choice needs to be a number, please try again");
    }

    // Json

  3. #3
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    Default Re: java.lang.numberformatexception error

    where do i put the try catch code? do i replace part of mine with it, or place within my code????

  4. #4
    Super Moderator Json's Avatar
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    Default Re: java.lang.numberformatexception error

    See the PM I sent you.

    // Json

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