Objects II Concepts

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Introduction

Today we are looking at what you can do with objects. We will cover:

Declarations
Anonymous Objects
Constructors

Declarations

In Java, a class provides the blueprint for objects, so you can create an object from a class. There are many different ways you can create an object. We will show the most common way below:

                        
                            public class myClass{

    String name = "JaysCodes";

    public static void main(String[] args){

        myClass obj = new myClass();
        System.out.println(obj.name);

    }

}

// Output
"JaysCodes"

Got it? Good! You can do this for arrays and ints in the format above too, for example!

Anonymous Objects

Anonymous simply means nameless. An object which has no reference is known as an anonymouso object. It can be used at the time of object creation only.

Below is how you can declare an anonymous object:

                        
                            class Calculator{
    void factorial(int n){
        int factorial = 1;
        for(int i=1; i<=n; i++){

            factorial=factorial*i;

        }

        System.out.println("Factorial is" + factorial);
    }

    public static void main(String args[]){

        new Calculaton().factorial(4);
        // calling method with anonymous object

    }
}

// Output
Factorial is 24

Constructors

A constructor initializes an object when it is created. It has the same name as its class and is syntactically similar to a method. However, constructors have no explicit return type.

Constructors are used to give initial values to the instance variables defined by the class, or to perform any other start-up procedures required to create a fully formed object.

                        
                            public class Cat{

    public Cat(){

    }

    public Cat(String name){
        //this is a constructor with one parameter, name
    }

}

Above is how to make a constructor, you can also do this for objects too. Every time a new object is created, at least one constructor will be invoked.

Sources: (click on them to see them)

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