Apex: How to Fix 'System.ListException: List index out of bounds' Error

How to Check If a List Is Empty Before Accessing Elements

Before referencing the 0th index of a list, always check whether the list contains records. The following Apex example shows how to guard against this error using a size check. The code only processes lstAccount[0] if the list contains at least one record:

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!!

Common Causes of List index out of bounds Error

• The SOQL query returned no rows to the List after execution.
• The code references fields on a List element at an index that does not exist (for example, index 0 when the list is empty).
• The List is populated in one context but accessed in a trigger or class where the query conditions do not match any records.