Difference between Integer and int in Java

Question

What is the difference between int and Integer in Java ? I know that "Integer" is a class and "int" is a datatype but they both work the same. Can they be used interchangeably ?

Answer 1

An int is a 32 bit integer that is represented internally as a 4 byte primitive. An Integer is a Java object that represents an int value. Integer instances are needed when working with the Collections API, as the collections only work with objects and not primitives. Integer also contains a bunch of useful methods that make working with them somewhat easier. The downside of using Integer is that it uses roughly 4 times the memory of the primitive version.