10.2. Operator overloading

Operator overloading is a new concept to Java developers since Java doesn't allow operator overloading. ^{[3], [4]}

^[3] Some Java programmers may want to argue that the + operator in Java is a pseudo-overloaded operator when it is used for concatenating strings. This is a special case whereby the compiler actually decides if you are doing a numerical addition or a string concatenation depending on the operand types, and hence shows a little 'operator overloading' behavior.

^[4] Operator overloading is a feature in C++ though.

In brief, operator overloading allows you to write special methods (called operators, or operator methods) which are invoked when an overloaded operator is used to perform an operation on one or more operands. For example, you can overload the + operator so that you can 'add up' two objects of type Matrix (Matrix may be a user-defined class which represents a matrix). The following statements will then make sense:

Matrix m1 = new Matrix();
Matrix m2 = new Matrix();
// + operator overloaded to accept Matrix operands
Matrix m3 = m1 + m2;

Operator overloading is an elegant way of allowing programmers to perform 'operations' on classes in a more intuitive way. Java does not support operator overloading.

More information about operator overloading can be found in Chapter 22.