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Thread: java.lang.ArrayIndexOutOfBoundsException - huh?

  1. #1
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    Default java.lang.ArrayIndexOutOfBoundsException - huh?

    Hi everyone. I am currently taking a beginners course in java programming at the university of Aarhus. We are now 2 weeks in to the course and our teacher has suggested that we should start some small projects to work on, on our own. So i have decided to try and write a bubblesort algorithm.
    Now i havenīt really gotten very far yet but i am getting a failure-message called

    "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3
    at bubbleSort.main(bubbleSort.java:20)"


    I basically do not understand why i am getting it. I hope that someone can explain it to me. And please keep in mind that you may have to "dumb it down" for me since i am only 2 weeks in to the course. I have already tried to look it up here ArrayIndexOutOfBoundsException (Java 2 Platform SE v1.4.2) and i still don't get it.

    import java.util.Vector;
     
    public class bubbleSort {
     
    	public static void main(String[] args) {
     
    		String[] name={"Thor", "Jensen", "Soeren"};
     
    		Vector v = new Vector();
     
    		int zero=0;
    		int one=1;
     
    		int runTimes = name.length;
     
    		while(runTimes>0){
    			if(name[zero].length() >= name[one].length()){      
    				v.insertElementAt(name[zero], 0);
    				zero++;
    				one++;
    				runTimes--;
    			} else {
    				v.insertElementAt(name[one], 0);
    				zero++;
    				one++;
    				runTimes--;
    			}
    		}
     
    		System.out.println(v);
    	}
     
    }
    Last edited by mrUnknown; February 14th, 2012 at 03:33 PM.


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    Default Re: java.lang.ArrayIndexOutOfBoundsException - huh?

    Your array has 3 elements, so valid indexes are 0, 1 and 2. You index it with 'zero' which you only increment (with 'zero++'). What do you want to happen when zero reaches 3? Try 'instrumenting' your code with lines like:
    System.out.println("zero is " + zero + ", one is " + one + ", runTimes is " + runTimes)
    so that you can see how the variables change in value as the code loops.

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    Default Re: java.lang.ArrayIndexOutOfBoundsException - huh?

    okay, iīll try that .. But since iīve already defined zero as 0 should i not then be able to use as index? or maybe you cannot use variables for this? When zero reaches 3 i want the loop to start over, but i must admit that i havenīt really figured out how to do that yet.

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    Default Re: java.lang.ArrayIndexOutOfBoundsException - huh?

    Your getting java.lang.ArrayIndexOutOfBoundsException because of your variable one.. you initialize it with a value 1.. so When the condition is satisfied the value of your variable one will be greater than the size of your array..

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