Review of variables

• A variable is a storage location. It has a specified type and (usually) a name. A variable declaration includes its name and its type and may also include an initial value (following the assignment operator =).
• Instance (member) variables are declared in a class definition. Every time an object which is an instance of the class is created, it gets a new instance of the member variable. Changing the value of the instance variable for one object does not affect the value of the variable for other objects.
• Class variables are also declared in a class definition. Unlike instance variables, they belong to the whole class; that is, only one storage location is created, and the variable has only value for all instances of the class.
• Parameters are variables which name arguments passed to methods or constructors. Whenever the method or constructor is called (invoked), a new parameter variable is created for each of the parameters in the method or constructor. Each parameter variable is initialized to the corresponding argument value in the expression calling the method or constructor. Once the body of the method or constructor has been executed, the parameter variables effectively cease to exist.
• Local variables may be created inside any block (expressions between {}s) or at the beginning of a for expression. They may be initialized when they are declared. A new local variable is created each time the block or for expression is entered. When the execution of the block or for expression is complete, the local variable effectively ceases to exist.

© 2004. Indiana University and Michael Gasser. www.indiana.edu/~gasser/Q530/Notes/variables.html 22 Sep 2004