Question

In searching a pre-populated ArrayList, call it

List<String> myList= new ArrayList<String>();

I am trying to add new elements to it based on these elements containing certain regex values. I am having success when I just need to return one substring of the element. For example, if I have

String removable = "X";

which resides in an element, call it

ABCDX

the X is easily removed and added to the ArrayList with the code

   if(myList.get(i).length() == 5 && myList.get(i).substring(4,5).contains(removable))
   {
            myList.add(i+1, myList.get(i).substring(0, 4));
   }

but when I have an element such as

ABXCD ,

which I presumed could be handled with

 if(myList.get(i).length() == 5 && myList.get(i).substring(2,3).contains(removable))
   {
            myList.add(i+1, myList.get(i).substring(0, 2).substring(3, 5));
   }

I get a String Index Out of Bounds Exception. How can this be rectified?

Answer 1

In your second code example you are using

abc1List.get(i)

should this not be

myList.get(i)

Edit

I believe your problem is that you are substring’ing a substring. Your code does this

myList.get(i).substring(0, 2).substring(3, 5)

So what that is saying is, get the substring of a string, then get a substring of the previously retrieved substring. Since the first substring is only 2 characters long, the second substring returns out of bounds as you are trying to start from index 3 which does not exist.

Your code pretty much evaluates to:

"ABXCD ,".substring(0,2) = "AB"

"AB".substring(3,5) = Out of bounds substring retrieval!

You need to do something like

myList.get(i).substring(0, 2) + myList.get(i).substring(3, 5)

or find an alternative method of doing what you want.