Object and Class in Java

Let’s discuss the core thing on which we been and going to write the Java Programs. Those are OBJECT and CLASS.

Object defines the state, behavior, and identity of a subsistence is technically known as an entity.

State: represents data (value) of an object.

Behavior: represents the behavior (functionality) of an object such as deposit, withdraw, etc.

Identity: Object identity is typically implemented via a unique ID. The value of the ID is not visible to the external user. But it is used internally by the JVM to identify each object uniquely.

       Take a real life example: let’s take a Pen and relate the same with above, the pen is an object with some name say “Parker”, it has some color say “Red” these properties are termed as “State”, the pen is used for “writing” so writing is the “Behavior”  and the pen will be having a cap, refill nib etc. can be called the Identity.

A class is a group of objects that has common properties. It is a template or blueprint from which objects are created.

A class in java can contain:

·         data member

·         method

·         constructor

·         block

·         class and interface

Syntax to declare a class:

class <class_name> {

    data member;

    method;

}

Instance variable in Java

A variable that is created inside the class but outside the method is known as an instance variable. Instance variable doesn't get memory at compile time. It gets memory at runtime when an object (instance) is created. That is why it is known as an instance variable.

Method in Java

In Java, a method is like function i.e. used to expose the behavior of an object.

Advantage of Method

·                                    Code Reusability

·                                    Code Optimization

·                                   new keyword

The new keyword is used to allocate memory at runtime.