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Thread: NullPointerException...how?

  1. #1
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    Default NullPointerException...how?

    I bet this will be an easy diagnosis but I can't seem to find why I am getting a NullPointerException. I used to make things like this all the time so it's extra weird. Any help will be appreciated.

    import java.util.Scanner;
     
    public class Main {
     
    private static Scanner input = new Scanner(System.in);
    private static String cmd;
     
    	public static void main(String[] args){
    		while(true/*!cmd.equals("quit")*/){
    			cmd.equals(input.nextLine());
    			processCommand();
    		}
     
    	}
     
    	//processes commands. Just testing right here ATM
    	public static void processCommand(){
    		if(cmd.equals("hi")){
    			System.out.println("boo");
    		}
    	}

  2. #2
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    Default Re: NullPointerException...how?

    Looks like there was an attempt to access a variable that has a null value.
    What line did the error message report? What variable(s) are on that line? Which one(s) have a null value?

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    Default Re: NullPointerException...how?

    Exception in thread "main" java.lang.NullPointerException
    at myname.youllmakefunofmeifyouseethisnamesoIwortethi sinstead.Main.main(Main.java:19)

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    Default Re: NullPointerException...how?

    The error message tells you the NPE occurs on line 19. So look at the variables on that line to find out which one is null. Then fix it. On the previous line add one or more print statements to print out all variables to find out which one is null.
    Improving the world one idiot at a time!

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    Default Re: NullPointerException...how?

    Line 19 is the cmd.equals(input.nextLine()); So I should set it as something useless then?

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    Default Re: NullPointerException...how?

    Huh?
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    Default Re: NullPointerException...how?

    **removed**
    Last edited by jps; August 13th, 2013 at 02:01 AM. Reason: spoonfeeding

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    Default Re: NullPointerException...how?

    Quote Originally Posted by illusionust View Post
    Line 19 is the cmd.equals(input.nextLine()); So I should set it as something useless then?
    Note that this line does not give cmd a value, but attempts to call a method on the variable cmd

    @divcret Please see The problem with spoonfeeding

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