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Objects are never created implicitly but instead are always passed or assigned by a reference variable. (Methods in Java are always pass by value, however, it is the value of the reference variable that is being passed.) [11] The Java Virtual Machine manages garbage collection so that objects are cleaned up after they are no longer reachable ...
A reference variable, once declared and bound, behaves as an alias of the original variable, but it can also be rebounded to another variable by using the reference assignment operator = ref. The variable itself can be of any type, including value types and reference types, i.e. by passing a variable of a reference type by reference (alias) to ...
Boxing's most prominent use is in Java where there is a distinction between reference and value types for reasons such as runtime efficiency and syntax and semantic issues. In Java, a LinkedList can only store values of type Object. One might desire to have a LinkedList of int, but this is not directly possible.
The capturing of final variables enables capturing variables by value. Even if the variable to capture is non-final, it can always be copied to a temporary final variable just before the class. Capturing of variables by reference can be emulated by using a final reference to a mutable container, for example, a one-element array. The local class ...
The default implementation of Object.clone() performs a shallow copy. When a class desires a deep copy or some other custom behavior, they must implement that in their own clone() method after they obtain the copy from the superclass. The syntax for calling clone in Java is (assuming obj is a variable of a class type that has a public clone ...
Comparison of programming languages; General comparison; Assignment; Basic syntax; Basic instructions; Comments; Control flow Foreach loops; While loops; For loops
Some people (including Guido van Rossum himself) have called this parameter-passing scheme "call by object reference". An object reference means a name, and the passed reference is an "alias", i.e. a copy of the reference to the same object, just as in C/C++. The object's value may be changed in the called function with the "alias", for example:
Using this technique, when a user asks the system to copy an object, it instead merely creates a new reference that still points to the same object. As soon as a user attempts to modify the object through a particular reference, the system makes a real copy, applies the modification to that, and sets the reference to refer to the new copy.