I am trying to read a txt file into an array but get an OutOfBoundsException(0)

Question

public static double [] loadGravityData( ) throws IOException
{
  File fileName = new File("gravity1.txt");
  Scanner inFile = new Scanner(fileName);

  double [] gravityData = {};
  while(inFile.hasNext())
   {    

   for(int i = 0; i <= gravityData.length; i++)
    {
     gravityData[i] = inFile.nextDouble();

    }

   }  
   inFile.close();

return gravityData;
}

The gravityData of i part is what is returning the exception. Any help would be much appreciated.

possible duplicate of [Declare array in Java?](http://stackoverflow.com/questions/1200621/declare-array-in-java) — OldProgrammer, Mar 10 '15 at 16:27
by doing `double [] gravityData = {};` you have a zero-length array — gtgaxiola, Mar 10 '15 at 16:29

nadavge · Answer 1 · 2015-03-10T16:33:25.883

1

You should initialize the array to be as long as the amounts of items you wish to read, and change

for(int i = 0; i <= gravityData.length; i++)
...

to

for(int i = 0; i < gravityData.length; i++)
...

This is because an array of length n has elements at 0,1,...,n-1.

If you count them you can tell that there are in fact n elements.

Edit, thanks Trengot

If you don't know how many items there are to read in advance, I suggest you look at ArrayList, which is a generic dynamic array type

edited Mar 10 '15 at 16:33

answered Mar 10 '15 at 16:26

nadavge

590
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Unless you're using concurrency, a `List` such as `ArrayList` would be better than `Vector`. – Holloway Mar 10 '15 at 16:33
@Trengot You're right, I haven't programmed Java in a while and got used to vectors of C++. Edited! – nadavge Mar 10 '15 at 16:35
I changed the <= to < and i get the same thing – harley Mar 11 '15 at 15:33
Did you change the rest as well? (Allocate the array or alternatively use an ArrayList?) – nadavge Mar 11 '15 at 19:05

score 0 · Answer 2 · answered Mar 10 '15 at 16:29

0

where are you allocating the array? In Java, arrays are of a fixed length and they do not auto-expand. In your case, you should use an ArrayList instead.

Additionally, you should change the <= to <

answered Mar 10 '15 at 16:29

amahfouz

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The additionally part of this is the cause of the error. The rest should be the aside. – Holloway Mar 10 '15 at 16:31

I am trying to read a txt file into an array but get an OutOfBoundsException(0)

2 Answers2