Class
A blueprint defining the charactaristics and behaviors of an object of that class type. Class names should be written in CamelCase, starting with a capital letter.
class MyClass{
...
}
Each class has two types of variables: class variables and instance variables; class variables point to the same (static) variable across all instances of a class, and instance variables have distinct values that vary from instance to instance.
Class Constructor
Creates an instance of a class (i.e.: calling the Dog constructor creates an instance of Dog). A class can have one or more constructors that build different versions of the same type of object. A constructor with no parameters is called a default constructor; it creates an object with default initial values specified by the programmer. A constructor that takes one or more parameters (i.e.: values in parentheses) is called a parameterized constructor. Many languages allow you to have multiple constructors, provided that each constructor takes different types of parameters; these are called overloaded constructors.
class Dog{ // class name
static String unnamed = "I need a name!"; // class variable int weight; // instance variable String name; // instance variable String coatColor; // instance variable Dog(){ // default constructor this.weight = 0; this.name = unnamed; this.coatColor = "none"; } Dog(int weight, String color){ // parameterized constructor // initialize instance variables this.weight = weight; // assign parameter's value to instance variable this.name = unnamed; this.coatColor = color; } Dog(String dogName, String color){ // overloaded parameterized constructor // initialize instance variables this.weight = 0; this.name = dogName; this.coatColor = color; } }
Method
A sort of named procedure associated with a class that performs a predefined action. In the sample code below, returnType will either be a data type or if no value need be returned. Like a constructor, a method can have or more parameters.
returnType methodName(parameterOne, ..., parameterN){ ... return variableOfReturnType; // no return statement if void }
Most classes will have methods called getters and setters that get (return) or set the values of its instance variables. Standard getter/setter syntax:
class MyClass{
dataType instanceVariable; ... void setInstanceVariable(int value){ this.instanceVariable = value; } dataType getInstanceVariable(){ return instanceVariable; } }
Structuring code this way is a means of managing how the instance variable is accessed and/or modified.
Parameter
A parenthetical variable in a function or constructor declaration (e.g.: in int methodOne(int x), the parameter is int x).
Argument
The actual value of a parameter (e.g.: in methodOne(5), the argument passed as variable x is 5).