Core Java Interview Question

What is OOPS?

OOP is the common abbreviation for Object-Oriented Programming.

Describe the principles of OOPS.

There are three main principals of oops which are called Polymorphism, Inheritance and Encapsulation.

Explain the Encapsulation principle.

Encapsulation is a process of binding or wrapping the data and the codes that operates on the data into a single entity. This keeps the data safe from outside interface and misuse. One way to think about encapsulation is as a protective wrapper that prevents code and data from being arbitrarily accessed by other code defined outside the wrapper.

Explain the Inheritance principle.

Inheritance is the process by which one object acquires the properties of another object.

Explain the Polymorphism principle.

The meaning of Polymorphism is something like one name many forms. Polymorphism enables one entity to be used as as general category for different types of actions. The specific action is determined by the exact nature of the situation. The concept of polymorphism can be explained as "one interface, multiple methods".

Explain the different forms of Polymorphism.

From a practical programming viewpoint, polymorphism exists in three distinct forms in Java:

Method overloading

Method overriding through inheritance

Method overriding through the Java interface

What are Access Specifiers available in Java?

Access specifiers are keywords that determines the type of access to the member of a class. These are:

Public

Protected

Private

Defaults

Describe the wrapper classes in Java.

Wrapper class is wrapper around a primitive data type. An instance of a wrapper class contains, or wraps, a primitive value of the corresponding type.

Following table lists the primitive types and the corresponding wrapper classes:Primitive Wrapper

boolean java.lang.Boolean

byte java.lang.Byte

char java.lang.Character

double java.lang.Double

float java.lang.Float

int java.lang.Integer

long java.lang.Long

short java.lang.Short

 

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