How is the conversion of reference types to primitive types and vice versa carried out?

In Java (and Android), conversion between reference types (wrappers) and primitive types is called auto-boxing and auto-unboxing.

• Boxing — converting a primitive type to its corresponding wrapper object. For example, int to Integer.
• Unboxing — converting a wrapper object back to a primitive.

Example:

int a = 5;
Integer boxed = a;       // auto-boxing
int b = boxed;           // auto-unboxing

Previously, you had to do this explicitly:

Integer boxed = Integer.valueOf(a);
int b = boxed.intValue();

Auto-boxing and auto-unboxing simplify working with collections and methods that require objects instead of primitives.