Java Autoboxing

Internal

• Java

Overview

Java has a mechanism called boxing that converts primitive types (such as int) into their corresponding reference wrapper types (java.lang.Integer). The opposite operation, converting reference types into their corresponding primitive types is called unboxing.

Autoboxing is a mechanism that performs boxing and unboxing automatically.

Autoboxing comes with a performance cost. Boxed values are wrappers around primitive types, and are stored on the heap. Therefore, boxed values use more memory and requires additional memory lookups to fetch the wrapped primitive type.

Wrapper Classes

java.lang.Byte

Java has a wrapper class named java.lang.Byte that provide a reference type representation to the primitive data type byte.

java.lang.Integer

Java has a wrapper class named java.lang.Integer that provide a reference type representation to the primitive data type int.

java.lang.Long

Java has a wrapper class named java.lang.Long that provide a reference type representation to the primitive data type long.

Autoboxing and Streams API

The Streams API has specialized stream types and API calls for primitive types, to avoid unnecessary autoboxing.

Performance Considerations

The performance penalty associated with autoboxing is quite significant. An operation on a large stream that uses boxed values uses on average 550% more time than the same operation on the corresponding specialized stream.

TODO

• https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html