Difference between int and Integer. The key difference between the Java int and Integer types is that an int simply represents a whole number, while an Integer has additional properties and methods.

Integer types. Java supports four integer types for space and precision reasons: byte integer, short integer, integer, and long integer. Arrays based on shorter integers don’t consume as much space.

Everything in Java is an object, except primitives like int. Turns out that small caveat has big implications for the language, ... Figure 2. A dense object in memory. Java performance pain points.