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OOP Interview Questions Answers

Question 1 : What do u meant by “SBI” of an object?

Answer 1 : SBI stands for State, Behavior and Identity. Since every object has the above three. State: It is just a value to the attribute of an object at a particular time. Behaviour:It describes the actions and their reactions of that object.Identity: An object has an identity that characterizes its own existence. The identity makes it possible to distinguish any object in an unambiguous way, and independently from its state.

Question 2 : Differentiate between the message and method.

Answer 2 : Message * Objects communicate by sending messages to each other. * A message is sent to invoke a method. Method * Provides response to a message. * It is an implementation of an operation.

Question 3 : Differentiate between a template class and class template.

Answer 3 : Template class: A generic definition or a parameterized class not instantiated until the client provides the needed information. It’s jargon for plain templates. Class template: A class template specifies how individual classes can be constructed much like the way a class specifies how individual objects can be constructed. It’s jargon for plain classes.

Question 4 : What are inner class and anonymous class?

Answer 4 : Inner class : classes defined in other classes, including those defined in methods are called inner classes. An inner class can have any accessibility including private. Anonymous class : Anonymous class is a class defined inside a method without a name and is instantiated and declared in the same place and cannot have explicit constructors.

Question 5 : What is multithreading?

Answer 5 : Multithreading is the mechanism in which more than one thread run independent of each other within the process.

Question 6 : What is a modifier?

Answer 6 : A modifier, also called a modifying function is a member function that changes the value of at least one data member. In other words, an operation that modifies the state of an object. Modifiers are also known as ‘mutators’. Example: The function mod is a modifier in the following code snippet: class test { int x,y; public: test() { x=0; y=0; } void mod() { x=10; y=15; } };

Question 7 : List out some of the object-oriented methodologies.

Answer 7 : Object Oriented Development (OOD) (Booch 1991,1994). Object Oriented Analysis and Design (OOA/D) (Coad and Yourdon 1991). Object Modeling Techniques (OMT) (Rumbaugh 1991). Object Oriented Software Engineering (Objectory) (Jacobson 1992). Object Oriented Analysis (OOA) (Shlaer and Mellor 1992). The Fusion Method (Coleman 1991).

Question 8 : Differentiate persistent & non-persistent objects?

Answer 8 : Persistent refers to an object’s ability to transcend time or space. A persistent object stores/saves its state in a permanent storage system with out losing the information represented by the object. A non-persistent object is said to be transient or ephemeral. By default objects are considered as non-persistent.  

Question 9 : Differentiate Aggregation and containment?

Answer 9 : Aggregation is the relationship between the whole and a part. We can add/subtract some properties in the part (slave) side. It won’t affect the whole part. Best example is Car, which contains the wheels and some extra parts. Even though the parts are not there we can call it as car. But, in the case of containment the whole part is affected when the part within that got affected. The human body is an apt example for this relationship. When the whole body dies the parts (heart etc) are died.

Question 10 : What is the difference between superclass and subclass?

Answer 10 : A super class is a class that is inherited whereas sub class is a class that does the inheriting.

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