AP® Computer Science A glossary

Unboxing

Course: AP® Computer Science A Shows up in: Unit 4: Data Collections

The automatic conversion the compiler makes from a wrapper class object to its primitive value, such as Integer to int or Double to double.

Appears in the course and exam description (CED): 4.7.A.3

It happens when a wrapper object is assigned to a variable of the primitive type, or passed to a parameter of that primitive type. Unboxing null throws a NullPointerException.

Integer stored = 12;
int plain = stored;
System.out.println(plain * 2);

Output:

24

Related terms

• Autoboxing
• Wrapper class
• Integer (class)
• Double (class)
• null