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How to Collect a Java Stream into a Primitive Collection: Bridging Without Boxing
When we’re working with Java Streams, converting them into Collections is a common task. If you’re dealing with objects like Integer or Double, you can just use .collect(Collectors.toList()) and things are simple. But, what if you want to deal with raw numbers like int or double? Then, you need to avoid "boxing," which is when Java wraps primitive types like int into their object equivalents like Integer. This wrapping can slow down your program and use more memory than necessary.
In this how-to guide, we’ll explore a more efficient way of collecting Java Streams into primitive collections while avoiding the performance hit caused by boxing.
Understanding Boxing and Primitive Collections
In Java, “boxing” is the automatic conversion that the compiler makes between the primitive types and their corresponding object wrapper classes. For example, converting an int to an Integer, or a double to a Double. The reverse process is called "unboxing". Whilst boxing makes it easier to work with primitive data in collections and generic data structures, it also introduces performance overhead.
Primitive collections are specialized data structures that store the primitive types directly, without wrapping them in…