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Chapter 4 - Unit 1

Data Types in Java

Class 8 - APC Understanding Computer Studies with BlueJ


Multiple Choice Questions (Tick the correct answers)

Question 1

A constant which gives the exact representation of data is called a/an:

  1. variable
  2. literal
  3. identifier
  4. character

Question 2

The default value of the boolean data type is:

  1. "false"
  2. true
  3. false
  4. "true"

Question 3

Character literal is assigned to a:

  1. char variable
  2. char type literal
  3. string variable
  4. string literal

Question 4

A character literal is enclosed in:

  1. ' 'Answer
  2. " "
  3. : :
  4. { }

Question 5

A set of characters is assigned to a:

  1. String variable
  2. Static variable
  3. Boolean variable
  4. None

Question 6

The ASCII codes of upper case alphabets range from:

  1. 65 - 90
  2. 60 - 85
  3. 65 - 91
  4. 97 - 122

Question 7

Which of the following is false to find square of a number?

  1. Math.pow(a,2)
  2. a*a
  3. Math.sqrt(a,2)
  4. All

Question 8

What type of value is returned by the sqrt function?

  1. int
  2. float
  3. double
  4. All

Question 9

Which of the following syntax is true to find the square root of a number?

  1. sqrt(a)
  2. Math.sqrt(a)
  3. Squareroot(a)
  4. None

Question 10

Boolean data is used to test a particular condition, i.e., true or false. Which of the following is a correct representation?

  1. boolean m = true
  2. boolean m = 'true'
  3. boolean m = "true"
  4. none

Short Answer Questions

Question 1

Write down the syntax for the following functions in Java programming:

(a) To find the smaller between two numbers.

Answer

Math.min(a, b)

(b) To find the absolute value of a number.

Answer

Math.abs(a)

(c) To find the exponent of a number.

Answer

Math.exp(a)

(d) To find the square root of a number.

Answer

Math.sqrt(a)

Question 2

Assign the value of pie () to a variable with the suitable data type.

Answer

double pi = 3.14159

Question 3

Give the output of the following expressions:

(a) If x = -9.99, calculate Math.abs(x);

Answer

9.99

(b) If x = 9.0, calculate Math.sqrt(x);

Answer

3.0

Question 4

Perform the following functions with a suitable data type to:

(a) assign 35.0012 to a variable.

Answer

double a = 35.0012;

(b) assign the value of √2 = (1.414) to a variable.

Answer

double a = Math.sqrt(2);

(c) assign 435.0 to a variable.

Answer

double a = 435.0;

(d) find the square root of 99 with a variable.

Answer

int a = 99;
double res = Math.sqrt(a);

(e) find the natural log of 23 with a suitable variable.

Answer

int a = 23;
double res = Math.log(a);

Question 5

Correct the given snippet:

int a = 45.1;
float b = 15.05;
double c = 92;
sum = 0;
sum = (a+b)*c/2;
System.out.println("The answer ="+ans);

Answer

Errors in the snippet
  1. a is an int variable so a floating point literal can't be assigned to it. a should be of double type.
  2. b is float variable but 15.05 is double literal. We need to convert 15.05 to float literal by appending f to it.
  3. Variable sum is not declared.
  4. In the last line, System.out.println("The answer ="+ans); we should print sum not ans.
Corrected Program
double a = 45.1;        //1st correction
float b = 15.05f;       //2nd correction
double c = 92;
double sum = 0;         //3rd correction
sum = (a + b) * c / 2;
System.out.println("The answer =" + sum);   //4th correction

Question 6

Write down the data type of the following:

(a) Integer ⇒ int

(b) Long Integer ⇒ long

(c) A fractional number ⇒ double

Long Answer Questions

Question 1

Define a variable.

Answer

A variable represents a memory location through a symbolic name which holds a known or unknown value of a particular data type. This name of the variable is used in the program to refer to the stored value.
Example:
int mathScore = 95;

Question 2

What is meant by a constant? Explain with an example.

Answer

The keyword final before a variable declaration makes it a constant. Its value can't be changed in the program.
Example:
final int DAYS_IN_A_WEEK = 7;

Question 3

What are the rules to assign a variable in Java programming?

Answer

  1. Name of the variable should be a sequence of alphabets, digits, underscore and dollar sign characters only.
  2. It should not start with a digit.
  3. It should not be a keyword or a boolean or null literal.

Question 4

Define the following:

(a) Compiler

Answer

A compiler is a program that translates a source program written in some high-level programming language into a target program in another low-level programming language without changing the meaning of the program. The compiler processes the complete source program at once and if there are compilation errors, they are all reported together at once.

(b) Interpreter

Answer

An interpreter is a program that reads a source program line by line, converts each line into its equivalent machine code and executes it. As it reads the program line by line so the errors are reported one by one.

(c) Byte code

Answer

Java compiler converts Java source code into an intermediate binary code called Bytecode. Bytecode can't be executed directly on the processor. It needs to be converted into Machine Code first.

Question 5

Distinguish between the following:

(a) Integer and Floating literal

Answer

Integer LiteralFloating Literal
Integer literal represents whole number values like 2, -16, 18246, 24041973, etc.Floating literal represents fractional numbers like 3.14159, -14.08, 42.0, 675.238, etc.
Integer literals are assigned to variables of data type — byte, short, int, long, charFloating literals are assigned to variables of data type — float, double

(b) Character and String literal

Answer

Character literalString literal
Character literals are written by enclosing a character within a pair of single quotes.String literals are written by enclosing a set of characters within a pair of double quotes.
Character literals are assigned to variables of type char.String literals are assigned to variables of type String.

(c) Source code and Object code

Answer

Source CodeObject Code
It is a set of statements in a High-Level programming language.It is a set of statements in Machine Language.
It is understood by human/programmer.It is understood by the processor.

(d) Compiler and Interpreter

Answer

CompilerInterpreter
It translates the whole source program into target program at once.It translates the source program into target program one line at a time.
All the errors found during compilation are displayed together at once.Errors are displayed line by line as each line is translated and executed.

Question 6

What is meant by primitive and non-primitive data types? Give an example of each.

Answer

Primitive data types are the basic or fundamental data types used to declare a variable. Examples of primitive data types in Java are byte, short, int, long, float, double, char, boolean.

A non-primitive data type is one that is derived from Primitive data types. A number of primitive data types are used together to represent a non-primitive data type. Examples of non-primitive data types in Java are Class and Array.

Question 7

Who developed Java? What was it initially called?

Answer

James Gosling developed Java and it was called Oak initially.

Question 8

Mention at least four features of Java.

Answer

Four features of Java are:

  1. It is an Object Oriented Programming Language.
  2. It is platform independent. It provides us Write Once, Run Anywhere (WORA) feature.
  3. It uses a compiler as well as an interpreter.
  4. It is case sensitive.

Question 9

What is a package? Give an example.

Answer

In Java, a package is used to group related classes. Packages are of 2 types:

  1. Built-In packages — These are provided by Java API
  2. User-Defined packages — These are created by the programmers to efficiently structure their code.

java.util, java.lang are a couple of examples of built-in packages.

Question 10

What is meant by implicit and explicit type conversion? Explain with an example.

Answer

In implicit type conversion, the result of a mixed mode expression is obtained in the higher most data type of the variables without any intervention by the user. Example:

int a = 10;
float b = 25.5f, c;
c = a + b;

In explicit type conversion, the data gets converted to a type as specified by the programmer. For example:

int a = 10;
double b = 25.5;
float c = (float)(a + b);

Question 11

Java program uses a compiler as well as an interpreter. Explain.

Answer

Java compiler compiles Java source code to Bytecode. Bytecode cannot run on the processor directly as processor only understands Machine Code. Java Virtual Machine (JVM) takes this Bytecode as input and converts it into Machine Code line by line. So, JVM acts as an interpreter for converting Bytecode to Machine Code. In this way, a Java program uses both a Compiler as well as an Interpreter to get executed on the processor.

Question 12

Java is case sensitive. Explain.

Answer

Java is case sensitive means that it distinguishes between upper case and lower case characters. Consider the below code snippet:

int studentMarks;
StudentMarks = 85;

This will give a compilation error as Java will treat studentMarks and StudentMarks as two different variables because the case of the characters is not same in both.

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