Arraylist - how can I check if an index exists?

java

index-validation

arraylist

exception-handling

byAnton Shumikhin·Jan 26, 2025

Verify an index's existence in an ArrayList with the following code:

You can use to perform the check:

if (index >= 0 && index < list.size()) {
  // index exist! Celebrate! 🥳
} else {
  // index doesn't exist. So sad 😢
}

This ensures the index is within the bounds of 0 to size()-1. Anything outside this range will feel unwanted and cause an IndexOutOfBoundsException.

Check The Index: A Step-By-Step Guide

The validity of the index in Java ArrayLists is crucial to remember to avoid office bets on how many times your code crashes.

Why do we Validate Indices?

Validating indices is not a fad. It has serious benefits for your code:

Data Integrity: Checking that the index is valid is like donning protective gear. It maintains your data's integrity.
Avoiding Runtime Exceptions: Your program could crash from a high IndexOutOfBounds cliff. So let's keep it on the flatland.

Safety in Accessing Data

Here are some truly genius ways to access the data in your ArrayList:

Pre Validation: Check list.size() against the index and wave IndexOutOfBoundsException goodbye. 🙋‍♂️
getOrNull usage: Use getOrNull(index), a lifeline for null-safe index checking. Obviously!
Dedicated Method: What's cleaner than an indexExists method? Maybe a nun's search history, but that's it.

The Raw Array Dilemma

When your code accesses data on every lunch break, make sure you're choosing the right lunch partner:

ArrayLists are flexible but may laze around.
Raw arrays' speed may win them the performance race.

Dealing with Exceptions and Advanced Techniques

So here's the dirt on handling that vicious IndexOutOfBoundsException:

Avoid Using Exceptions: Exceptions as control flow mechanism are not friendly. Remember, it's not you, it's them.
Dynamic Handling: If you're into experimental stuff, try using arrayList.get(index) in a try/catch block. Note: weigh the performance costs.
Do you Even Kotlin, Bro?: Leverage Kotlin's getOrNull(index) to allow null values when checking indices. Sweet!

Coding Conventions to Keep You Clean

Don't be messy! Here are some Java coding conventions that could qualify you for a Nobel:

Naming variables is art. Balance truth and beauty. int seatCount = arrayList.size(); is a masterpiece.
Utility Functions are to code what WD-40 is to a squeaky door. A separate method indexExists(ArrayList<?> list, int index) might save your sanity.

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