Classes

A class is essentially a data type. Whenever we create an instance of a class we declare it so say I want to declare 10 dog ages i would go and say

int dogAge1= 3; and say int dogAge2=12; This is inefficient and is a waste of time.

Within a class we have methods and we have attributes. An attribute is similar to variables in that they hold information for us.

We want to have 2 attributes for our dog class the Name and the age. Classes allow us to build very large application without having to code

every small bit by ourselves. We have a blue print of how sth might look. Say I have a person Class and wanted to describe a specific the person the details are ### what’s called attributes. If we wanted to build a large scale application we do not want to describe every single person specifically using a bunch of different ### variables. This would be a waste of time. Instead, we create a blueprint of what a person might look like.

We can say two fields:

- a name variable

- a talk method

The above idea is a structure of a person which is known as a class. To create a new person, all we have to do is instantiate the class. This process is called

an object. The class is the blueprint and the object is the specific example. A class allows us to create different entities which are similar in structure.

Classes will defined within a file and objects will be defined as variables.

Person x = new Person();

x is what’s called an identifier

A Class is a structure/blue print and object is an instance of the class. The above has a class name Person. Person here, is what's called a custom type

x is the identifier. When we instantiate we can create n number of objects say: Alan, Waleed, Neha, Michael, Juan

A field is just a variable within a class

The person class has two elements: Name: This is a field talk():

A field is essentially a variable that we can assign a value to.

When we instantiate the class into an object we can assign a value to the field name such as “Angela”

public class Vars
{
	//Variables outside of a method and within a class are called FIELDS!
	public int testFie=6;

	//So when some make an instance of the class Stupid Program the field testFie
	//Would be available for anyone and it would have a default value of 6.
	
    public class Main 
    { 
      // Instance Variables 
      String name; 
      String major; 
      String year; 

      // Constructor Declaration of Class 
      public Main(String name, String major, String year) 
      { 
          this.name = name; 
          this.major = major; 
          this.year = year; 
      } 

      // method 1 
      public String getName() 
      { 
          return name; 
      } 

      // method 2 
      public String getMajor() 
      { 
          return major; 
      } 

      // method 3 
      public String getYear() 
      { 
          return year; 
      } 

      @Override
      public String toString() 
      { 
          return("Hi my name is "+ this.getName()+ 
                 ".\nMy major is " + 
                 this.getMajor()+", and I am a " + this.getYear());
      } 
  
      public static void main(String[] args) 
      { 
          Main carolina = new Main("carolina","CS", "Senior"); 
          System.out.println(carolina.toString()); 
      }
    }
}