A boxed number, such as this instance of Integer, is nice because it can be treated as an object and has useful methods. However:

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

• Integer takes 4 to 6 times as much storage as an int.

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

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

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

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