Boxed Number

A boxed number, such as this instance of Integer, is nice because it can be treated as an object, used in structures such as LinkedList<Integer>, and has useful methods.

However:

• Integer has the same numeric accuracy as an int, 32 bits.

• Integer requires 16 bytes of storage, while int only requires 4 bytes.

• Integer is immutable: since it is possible that multiple variables point to it, we cannot change its value. Double, String, etc. are immutable.

• Doing arithmetic (even ++) may require creation of a new box (allocation of new storage), often making the old box garbage. (Java caches small Integer values to make them more efficient.)

• Boxes are somewhat expensive because they must be garbage collected. The garbage collector is a highly paid worker.