Classes and Objects

Class (Programming)

A class is a template or blueprint. Represents all similar objects of a kind.

• Each class has associated source code that defines attributes and methods.

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Object (Programming)

An object is an instance of a class / belongs to a particular class and has individual characteristics. Many distinct instances be created from a single class.

• Method

  A method is a procedure on an object which can be invoked. A method may have parameters to pass additional information. All methods have return types / values, a method may return void if no information is being handed back to the caller.

  A method implements the behaviour of objects, they have a consistent structure of a header and a body.

  • The header describes:
    • The visibility to objects of other classes.
    • Whether the method returns a result.
    • The name of the method.
    • Whether the method takes parameters.
  • The body encloses the body’s statements.

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• Class Attribute

  An object also has attributes, which are values stored in **fields**.

  The class defines what fields an object has, but each object stores its own set.

  State

  The state is the set of values of all fields of an object.

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• Method Signature

  Method signature: Consists of the function prototype and any relevant types.

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Note: for overloading, signature cannot be duplicated but name can be re-used.

Method signature is the method name and parameter types of a method. add(int v)

Method header: /*comment*/ public void add(int v)