It is a basic unit of Object-Oriented Programming and represents real life 

entities. A typical Java program creates many objects, which as you know,

interact by invoking methods. An object consists of : 

​

State: It is represented by attributes of an object. It also reflects the 

properties of an object.

​

Behavior: It is represented by methods of an object. It also reflects the 

response of an object with other objects.

​

Identity: It gives a unique name to an object and enables one object to 

interact with other objects. 

​

class Student

{ 

    int id;//data member (also instance variable) 

    String name; //data member (also instance variable) 

    public static void main(String args[])

    { 

        Student s1=new Student();//creating an object of Student 

        System.out.println(s1.id); 

        System.out.println(s1.name); 

     } 

} 

Remember from the Java Syntax chapter 

that a class should always start with an uppercase first letter, 

and that the name of the java file should match the class name.

ClassName obj = new ClassName(); //creating an object of ClassName class 

System.out.println(obj.field1); // calling field of the object (bad practice, make the fields private)

System.out.println(obj.field2);

​

obj.doSomething(); // calling method of the object

// Default behavior of toString() is to print class name, then

// @, then unsigned hexadecimal representation of the hash code

// of the object

​

public String toString()

{

    return getClass().getName() + "@" + Integer.toHexString(hashCode());

}

The Object class is the parent class of all the classes in java by default.In 

other words, it is the topmost class of java.

The Object class is beneficial if you want to refer any object whose type you 

dont know. Notice that parent class reference variable can refer the child 

class object, know as upcasting.

class Student{  

 //defining fields  

 int id;//field or data member or instance variable  

 String name;  

 //creating main method inside the Student class  

 public static void main(String args[]){  

  //Creating an object or instance  

  Student s1=new Student();//creating an object of Student  

  //Printing values of the object  

  System.out.println(s1.id);//accessing member through reference variable  

  System.out.println(s1.name);  

 }  

}  

Using new keyword.

Using new instance.

Using clone() method.

Using deserialization.

Using newInstance() method of Constructor class.