Revising Basic Java Concepts

Question 1

D: Procedural Programming Paradigm

Answer 1

Programming approach that focuses on the procedures for solving problems.

Question 2

D: Object

Answer 2

An object is an entity having specific characteristics,identity, and behaviour.
Also, instance of a class

Question 3

D: Class

Answer 3

A class is a blueprint representing objects having similar characteristics and behaviour

Question 4

D: Data Abstraction

Answer 4

Data Abstraction refers to the act of representing only the essential features without showing the background details or explanations.
Example: Switchboard

Question 5

D: Modularity

Answer 5

Modularity is the act of partitioning a program into individual components.

Question 6

D: Encapsulation

Answer 6

Encapsulation is the wrapping up of data and functions into a single unit called class.
Encapsulation is a way of implementing Abstraction.

Question 7

D: Inheritance

Answer 7

Inheritance is the ability of one class of things to inherit properties or capabilities from another class.
Example: class 'car' has inherits some of its properties from the class 'automobiles'.

Question 8

D: sub class or derived class

Answer 8

A class that inherits properties or capabilities from another class.

Question 9

D: base class or super class

Answer 9

A class from which another class inherits properties.

Question 10

D: Polymorphism

Answer 10

Polymorphism is the property by which a message can be sent to objects of different classes and each object can respond differently based on its class.

Question 11

How does java solve the problem of platform independence?

Answer 11

By using Bytecode

Question 12

Java bytecode is interpreted by a special java interpreter called …

Answer 12

Java Virtual Machine

Question 13

What are the most common java programs?

Answer 13

Applications and Applets

Question 14

What are Applications?

Answer 14

Applications are standalone programs that run independently of other programs or applications.

Question 15

What are Applets?

Answer 15

Applets are programs that run inside another application such as a web browser.

Question 16

What is initial class?

Answer 16

Initial class is the class in a java program that must have the same name as the java program file and it contains the main() method.
If there is one class in a java program it is the initial class

Question 17

Java uses the _________ character set.

Answer 17

Unicode. It is a two byte character set

Question 18

What are keywords?

Answer 18

Keywords are words which have special meaning in java. They are reserved for special purposes and must not be used for normal identifier names.
Example: final,int,etc.

Question 19

What are tokens?

Answer 19

TOKENS ARE THE SMALLEST INDIVIDUAL UNITS IN A PROGRAM.

Keywords,identifiers,literals,operators and punctuators are tokens in a java program.

Question 20

What are literals?

Answer 20

Literals (aka constants) are data items that have fixed values.

Question 21

What are the types of literals java allows?

Answer 21

1. Integer literals: whole numbers,can be written in decimal,octal or hexadecimal form
2. Floating-point literals: numbers having fractional(decimal) point. Can be written in fractional (0.00039) or exponential (0.39E-5)
3. Boolean literals: represented by true or false.
4. Character literals:single character or escape sequence enclosed by single quotation marks.
5. String literals: one or more characters enclosed in double quotation marks.
6. The null literal: represents null reference and is written as null

Question 22

What are identifiers?

Answer 22

Identifiers are names given to various program units by the programmer. They are the names of variables,classes,methods,etc.

Question 23

What are the rules that must be followed while forming identifiers?

Answer 23

1. Identifiers can have alphabets, digits, underscore and dollar sign,can be of any length.
2. Must not begin with a digit.
3. Must not be a keyword.
4. Java is case sensitive.

Question 24

What is a variable?

Answer 24

A variable is a named memory location which holds a data value of a particular data type.

Question 25

What is a constant value?

Answer 25

A constant value represents a named value that remains fixed throughout the program. A constant is declared in a similar way as a variable but with the final keyword.

Question 26

What are data types?

Answer 26

Data types are means to identify the type of data and associated operations of handling it.

Question 27

What are the categories of data types provided by java?

Answer 27

1. Primitive data types

2. Reference data types

Question 28

What are primitive data types?

Answer 28

Primitive data types are the data types that are provided by the language.
They are not based on any other data types.
They are also called FUNDAMENTAL or INTRINSIC DATATYPES

Question 29

What are reference datatypes?

Answer 29

They are datatypes that are created using primitive datatypes.
They are used to store memory address of an object.

Question 30

Name the primitive data types in java.

Answer 30

1. Numeric Integral:positive and negative whole numbers. Int,short,byte,long.
2. Floating point: can store fractional numbers.
   Float(precision of six digits) and double(precision of 15 digits).
   Java assumes fractional numbers as DOUBLE by default.
3. Character : used to store characters.
4. Boolean : represents a single true/false value.

Question 31

Name few reference data types in java.

Answer 31

Arrays,classes and interfaces.

Question 32

Reference is aka …….

Answer 32

Pointer or memory address in other languages

Question 33

What are the two values associated with a symbolic variable?

Answer 33

1. rvalue(data value)

2. lvalue(location value)

Question 34

What are the types of operators offered by java?

Answer 34

1. Arithmetic: +,-,*,/,%
2. Increment/Decrement: ++,–
   Prefix-change then use
   Postfix-use then change
3. Relational: aka comparison operators
   ,<=,>=,==,!=
4. Logical: &&,||,!
   combine 2or more relational operations for decision making
5. Shift operators