instance means just creating a reference(copy) .

object :means when memory location is associated with the object( is a runtime entity of the class)  by using the new operator

interface is a set of abstract methods, all of which have to be overriden by the class whichever implements the interface

abstract class is a collection of data and methods which are abstact  (not all of them)

Hi,

  Instance refers to the copy of the object at a particular time whereas object refers to the memory address of the class.

Interface supports runtime polymorphism,but abstract class doesn't.

All methods in interface have no defination, only declarations.But abstract class have methods with defination.

I think that abstract classes too support run-time polymorphism for the methods that are abstract within them. For such a case, the abstract class and interface provide similar functionality.

if i declare any fields in the classi.e not in any methods...they r given a default value,i.e for int its zero(0)..these are instance fields..........an object is an instance of a classi.e the object created is of the class type.

          well, in an interface you can only define the prototype of the methods,it cant contain any implimentations,while in an abstract class there can be absract methods and also implimentations of the method which are not abstract

Object is instance of a Class.

All variables of interface are by default static, final. Interface can not have implemented methods. All methods are by default abtract.

Abstract class should have at least one abstract method, other methods can have implementation.

Instance referes to Reference of an object.

Object is actaully pointing to memory address of that instance.

we can implement more than one interface.But We cannot extend more than one Abstract Class.

The main difference between abstract class and interface is,

1. Abstract class has the constructor, but interface doesn't have.

2. Main reason is abstract class contain the instance variable, that why it has
the constructor, where as interface has only constants (final variables and
ABSTRACT METHODS).

3. A class which can implement the interface, is not implement all methods which
are declared in interface , such class is declared as abstract class. that mean
abstract class is a subtype of an interface.

This is my conclusion. If you have an queries let me know.