'System.ListException: List index out of bounds' error

Check if list is empty

Before referring to the 0th index of a list, here is sample code to check on whether the list is empty or not.

List lstAccount = [Select Id, Name from Account Limit 10];
// Before processing the list check if its empty or not
// It will go inside the loop only if the List is having values in it.
if(lstAccount.size() > 0) {
 // Do something with lstAccount[0].Name
 }
// If you try to access lstAccount[0] without empty check then it will obviously throw that error!!