Question

Objects, classes, relationships, attributes, and methods

• Explain these five terms and how they are related.
• Then provide an example to illustrate the main ideas.

Answer 1

50. . Class is a user defined data type, which holds its own data members and member functions, which can be accessed and used by creating an instance of that class. A class is like a blueprint for an object.
50. Object is an instance of a Class. When a class is defined, no memory is allocated but when it is instantiated (i.e. an object is created) memory is allocated.
50. Attributes and methods are basically variables and functions that belongs to the class. These are often referred to as "class members"
50. Method in object-oriented programming is a procedure associated with a class. A method defines the behavior of the objects that are created from the class. Another way to say this is that a method is an action that an object is able to perform.
50. One of the advantages of Object-Oriented programming language is code reuse. This reusability is possible due to the relationship b/w the classes. Object oriented programming generally support 4 types of relationships that are: inheritance , association, composition and aggregation.
50. for example inhertiance, here we create a child class that can acces the functions and members of its parent class, thus these two classes have relationship between them

public class Car {

  // Create a fullThrottle() method

  public void fullThrottle() {

    System.out.println("The car is going as fast as it can!");

  }

  // Create a speed() method and add a parameter

  public void speed(int maxSpeed) {

    System.out.println("Max speed is: " + maxSpeed);

  }

  // Inside main, call the methods on the myCar object

  public static void main(String[] args) {

    Car myCar = new Car();     // Create a myCar object

    myCar.fullThrottle();      // Call the fullThrottle() method

myCar.speed(200);          // Call the speed() method

// The car is going as fast as it can!// Max speed is: 200

We created a custom Car class with the class keyword.

2) We created the fullThrottle() and speed() methods in the Car class.

3) The fullThrottle() method and the speed() method will print out some text, when they are called.

4) The speed() method accepts an int parameter called maxSpeed - we will use this in 8).

5) In order to use the Car class and its methods, we need to create an object of the Car Class.

6) Then, go to the main() method, which you know by now is a built-in Java method that runs your program (any code inside main is executed).

7) By using the new keyword we created a Car object with the name myCar.

8) Then, we call the fullThrottle() and speed() methods on the myCar object, and run the program using the name of the object (myCar), followed by a dot (.), followed by the name of the method (fullThrottle(); and speed(200);). Notice that we add an int parameter of 200 inside the speed() method.