CSA 3.5-3.9 Vocabulary

AP CSA Runestone Unit 3 3.5-3.9 Vocabulary

Instance Variables

define the attributes or data needed for objects

Methods

A block of code that performs a specific task. Defined inside a class and can access the instance variables of the class

Constructors

initializes the instance variables when the object is created

Object of the Class

Declare an object of your class in the main method or from outside the class.

Method Call

whenever you want to use the method, call objectName.methodName();

Method Definition

Write method header like following: public void methodName()

Return Statement

returns a variable’s value or an expression

Return Type

Type of value in the return statement that replaces the keyword void. Examples are String, int, double, and boolean.

Void Method

Does not return a value

Non Void Method

Returns a value

Return by Value

a return expression compatible with the return type is evaluated, and the value is returned

Accessor Method (Getter)

allows objects of other classes to obtain a copy of the value of instance variables or class variables. Is a non-void method.

Mutator (Modifier) Method/ Setter

a method that changes the values of the instance variables or class variables. It is often a void method.

Parameter

a variable in a method’s header that is used to pass in data that the method needs to do its job

Arguments

a value that is passed into a method when the method is called. It is saved into a parameter variable.

Anonymous Objects

When we create a new object without associating it with a variable

Call By Value

Used when it passes arguments to methods. This means that a copy of the value in the argument is saved in the parameter variable. It initializes the parameters with copies of the arguments. If the parameter variable changes its value inside the method, the original value outside the method is not changed.

Aliases

When two object references reference the same object

Mutable

their instance variables can change after they are constructed

Static or Class Methods

Methods that belong to the class and not to any object of the class

Static or Class Variables

Belong to the class, with all objects of a class sharing a single copy of the class variable and they use the keyword static

Final Keyword

Used in front of a variable declaration to make it a constant value that cannot be modified. Constants are traditionally capitalized.

Scope

Defined as where a variable is accessible or can be used. The scope is determined by where you declare the variable when you write your program.

Class Level Scope

instance variables inside a class

Method Level Scope

local variables (including parameter variables) inside a method

Block Level Scope

loop variables and other local variables defined inside of blocks of code with { }

Local Variables

Variables declared in the headers or bodies of blocks of code. Local variables can only be accessed in the block in which they are declared. Local variables that are declared inside a method are usually declared at the top of the method.

This Keyword

Acts as a special variable that holds a reference to the current object- the object whose method or constructor is being called. It can only be used in instance methods and constructors.