Converting from int to Integer is called boxing and converting back from Integer to int is called unboxing. In JDK 1.5+, both are automatic.

In code prior to JDK 1.1, you had to do a lot of manual tedious converting back and forth from primitive int to Integer Object, and similarly for byte/ Byte, char/Character, short/ Short, long/ Long, float/Float and double/ Double.

In JDK 1.5+, these conversions are inserted for you automatically. You still pay the time penalty for the conversions, it is just you don’t have to spell them out longhand.

Autoboxing will interconvert Integer and int transparently, but not Integer[] and int[]. That you will have to do yourself element by element.

Manual Vs AutoBoxing

AutoBoxing Example

Old Style Manual Boxing Example

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