How to use Google Guava's Preconditions.checkElementIndex?

Question

The api doc said: Ensures that index specifies a valid element in an array, list or string of size size.

But where pass the 'target' array or list string in this method?

Answer 1

The element inside the Array , List and String can be accessed using the 0-based index.

Suppose you want to access a particular element from a List using an index .Before calling list.get(index) , you may use the following to check this index is between 0 and list.size() to avoid IndexOutOfBoundsException :

 if (index < 0) {
        throw new IllegalArgumentException("index must be positive");
 } else if (index >= list.size()){
        throw new IllegalArgumentException("index must be less than size of the list");
 }

The purpose of Preconditions class is to replace this checking with the more compact one

Preconditions.checkElementIndex(index,list.size());

So , you don't need to pass the whole target list instance .Instead , you just need to pass the size of the target list to this method.