java.lang.IndexOutOfBoundsException: Index: 4, Size: 4 code example

Example: java.lang.indexoutofboundsexception: index: 0, size: 0

The problem is that you are using set method to update element at index 0

set(index,value) method needs an element to present at that index

but you haven't added any element at that position in medium arraylist before that .

So you need to first add an element at index 0 thereafter only you can update it with set method