For reference types, including Integer etc., == means equality of pointer values, i.e. same data address in memory.

Rule: To test equality of the contents of a reference type, use .equals().

Rule: To make an Integer, either use casting or Integer.valueOf()

• new Integer() always makes a new box, costing 16 bytes.

• Integer.valueOf() will reuse a value in the Integer cache if possible, costing 0 bytes.

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