Introduction to Object Class

Introduction to Object Class

Posted in : Core Java Posted on : October 6, 2010 at 3:51 PM Comments : [ 0 ]

This section describe about Object Class and it's implementation in java.

Introduction to Object Class

Objects basics

Click here to see objects basics

Object Class

  • All the classes defined are subclasses by default.
  • Object class is superclass of every class.
  • The inheritance happens automatically.
  • Your classes will inherit members from the class Object.

Given below some methods and their functions :

  Methods        It's Function   
toString() It returns a string which describe the current object. 
equals() It is used to compare two objects.
getClass() It returns the current object class.
hashCode() It is used to calculates a hashcode for an object.
notify() wakes up a thread associated with the current object.
notifyAll() wakes up all threads associated with the current object.
wait() causes a thread to wait.

Example :Getting class name of the object

class Sub {
	public Sub(String myname) {

public class ObjectClass {
	public static void main(String args[]) {
		Sub s = new Sub("Ankit");
		Class classname = s.getClass();

Output :

C:\Program Files\Java\jdk1.6.0_18\bin>javac

C:\Program Files\Java\jdk1.6.0_18\bin>java ObjectClass

Comparing Objects

In java, objects can be compared using 'equals' method as :

public class EmployeeMain {
	public static void main(String[] args) {
		Employee emp1 = new Employee("Divya", "Singh");
		Employee emp2 = new Employee("Ankit", "Kaushal");
		if (emp1.equals(emp2))
			System.out.println("These employees are the same.");
			System.out.println("These are different employees.");


class Employee {
	private String lastName;

	private String firstName;

	public Employee(String lastName, String firstName) {
		this.lastName = lastName;
		this.firstName = firstName;

	public String getLastName() {
		return this.lastName;

	public String getFirstName() {
		return this.firstName;

	public boolean equals(Object obj)

		if (this == obj)
			return true;
		if (this == null)
			return false;

		if (this.getClass() != obj.getClass())
			return false;

		Employee emp = (Employee) obj;
		return this.lastName.equals(emp.getLastName())
				&& this.firstName.equals(emp.getFirstName());

Output :

C:\Program Files\Java\jdk1.6.0_18\bin>javac

C:\Program Files\Java\jdk1.6.0_18\bin>java EmployeeMain
These employees are the same.

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