pass by value and pass by reference in Java?

[wolle]

What is the difference between pass by value and pass by reference in Java?

The parameter passing mechanism in Java is always by_value. The by_reference passing mechanism doesn't exist in Java. It means whatever you pass (a primitive or a reference) to a method it will be copied before it is available in the method.

It's important to understand that objects are always represented/handled indirectly by so called references in Java. A reference can be thought of as a "pointer" to an object. Therefore you could claim that "in Java an object is passed by its reference" but that doesn't mean the passing mechanism is by_reference (in the computer science sense of the term). So a reference is passed indeed but it is by_value, hence the confusion.