Classes and Objects

Today I learned how to make classes and objects. You must first define your class. Like I explained in earlier post, a class is a blueprint and an object is an instant of that class. In our game an example of a class would be body, and an object of that class would be the sun. When defining a new class you must type class then the name of your class. After that you must define certain aspects of your class. These aspects may include things like mass, density, and velocity. These are called instance variables.

When declaring objects you define those specific values for those instance variables. First you must make a new object by typing (class_name object_name = new class_name()). Just like when you’re making an array you must use the key word new when making an object. After you have created your object you can then define values to your instance variables. Extending the example above, you can make the mass = 34 and the velocity = 9. Below is another example where I made a class called Person with instance variables of age and name. Then I defined those variables for two objects.

class Person{

     

      // Instance variables (data or "state")

      String name;

      int age;

      // Classes can contain

      // 1. Data

      // 2. subroutines (methods)

}

public class Objectsclass {

      public static void main(String[] args) {

            Person person1 = new Person();

            person1.name = "Joe";

            person1.age = 33;

            Person person2 = new Person();

            person2.name = "Sarah";

            person2.age = 67;

            System.out.println(person1.age);

      }

}