Java Projects - Second Edition

Argument passing

In Java, arguments are passed by value. When the method modifies an argument variable, then only the copy of the original value is modified. Any primitive value is copied during the method call. When an object is passed as an argument, then the copy of the reference to the object is passed.

That way, the object is available to be modified for the method. In the case of classes that have their primitive counterpart, and also in the case of String and some other class types, the objects simply do not provide methods or fields to modify the state. This is important for the integrity of the language, and to not get into trouble when objects and primitive values automatically get converted.

In other cases, when the object is modifiable, ...