What is the difference between long and int in Java, and when should you use each?

General Discussions
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1

Sometimes I see APIs using long, Long, int, or Integer in Java, and I can’t figure out how the decision is made.

When should I choose long vs. int, and when should I use Long vs. Integer? What are the key differences and best practices for selecting the right type?

2

Alright, let’s break this down step by step! In Java, the main difference between long and int lies in their size and range. An int is a 32-bit signed integer, meaning it can hold values from -2,147,483,648 to 2,147,483,647. On the other hand, a long is a 64-bit signed integer, which supports much larger numbers, ranging from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807."

“So, when should you choose one over the other? Here’s a simple guideline:”

:white_check_mark: Use int when you’re working with smaller numbers, like counts, indexes, or small IDs. :white_check_mark: Use long when you expect larger values, such as timestamps, financial calculations, or unique identifiers like database IDs.

"In most cases, you’ll default to int unless you’re handling values that could exceed the int range. This is because int uses less memory and generally performs better on modern CPUs.

3

Nice breakdown! Now, let’s dive a bit deeper into the distinction between primitive types (like int and long) and their wrapper classes (like Integer and Long). You’ll often see Integer and Long in APIs, especially when working with collections, generics, or nullable types."

“Here’s when you’d want to choose the wrapper classes:”

:white_check_mark: Use Integer or Long when working with Java collections (like List<Integer> or Map<Long, String>), as generics don’t work with primitives.

:white_check_mark: Use Integer or Long if you need to handle null values, because int and long cannot be null.

:white_check_mark: Use int or long for performance-sensitive code, as primitives avoid the overhead of object creation and are more memory-efficient.

So, in short, if you’re dealing with a scenario where nullability is important (like interacting with a database or frameworks), you’ll likely choose Long. But if you’re writing performance-critical, CPU-bound code, long (primitive) is the way to go.

4

Absolutely! Now let’s dig into the performance and memory overhead. As mentioned earlier, Integer and Long are objects, and this brings additional memory consumption compared to their primitive counterparts like int and long."

Here’s a quick comparison to keep in mind:

  • int (4 bytes) vs. long (8 bytes): Choose wisely when memory efficiency is critical.
  • Integer and Long are objects, which add roughly 16 bytes of overhead for each instance due to Java’s object metadata.

Another key point is autoboxing/unboxing, which can impact performance. Whenever you convert a primitive to an object (or vice versa), Java adds some extra overhead, involving more CPU cycles.

So, if you’re processing millions of numbers in a loop, using Integer instead of int can cause a noticeable performance hit. However, if you’re working with frameworks like Hibernate, JSON libraries, or anything that requires objects, Long is usually unavoidable. Just be mindful of the trade-offs when dealing with large-scale applications!