Chapter 4

Operators in Java
Class 9 - APC Understanding Computer Applications with
BlueJ

Multiple Choice Questions

Question 1

The statement n += 4 is equivalent to:

1. ++n
2. n=n+4 ✓
3. n+1
4. none

Question 2

What will be the output of a & b in the following, if int a, b; a=10; b=a++;

1. 10,10
2. 10,11
3. 11,10 ✓
4. 11,11

Question 3

What will be the output of a++ when int a = -1;

1. 1
2. -1
3. 0 ✓
4. none

Question 4

If int a = 25, b = 5, c = 0; what value is stored in c? When c = a % b;

 1. 5.0
2. 5
3. 0 ✓
4. none

Question 5

What is the result of the following in Java statement?

int m=8;
m*=8;
System.out.println("The output =" + m);

1. 8
2. 64 ✓
3. 16
4. 88

Question 6

double c;
int x, y, z;
x = 5; y = 10; z = 11;
c = x*y+z/2;
The value stored in c is:

1. 55.0 ✓
2. 55.5
3. 55
4. none

Explanation

c=x*y+z/2
⇒ c = 5 * 10 + 11 / 2
⇒ c = 5 * 10 + 5
⇒ c = 50 + 5
⇒ c = 55.0

Question 7

int m, p;
m = 5;
p = 0;
p = m-- + --m;
The output will be:

1. 11
2. 10
3. 8 ✓
4. 12

Explanation

p = m-- + --m;
⇒p=5+3
⇒p=8

Question 8

int a=7, p=0, q=0;

p= ++a + --a;
q -= p;
The output of q will be:

1. 13
2. 14
3. 15
4. -15 ✓

Explanation

p = ++a + --a
⇒p=8+7
⇒ p = 15

q -= p
⇒q=q-p
⇒ q = 0 - 15
⇒ q = -15

Write the Java expressions for the following:

Question 1

p = a2 + bc
Answer

p=a*a+b*c

Question 2

m = a2 - b2 / (ab)

Answer

m = (a * a - b * b) / (a * b)

Question 3

s = ut + (1/2)at2

Answer

s = u * t + (1.0 / 2) * a * t * t

Question 4

f = uv / (u + v)

Answer

f = u * v / (u + v)

Question 5

(a + b)2 + b

Answer

(a + b) * (a + b) + b

Question 6

y = 2(lb + bh + lh)

Answer

y = 2 * (l * b + b * h + l * h)

Question 7
a2 + b2

Answer

a*a+b*b

Question 8

z = x3 + y3 - xy / 3

Answer

z=x*x*x+y*y*y-x*y/3

Answer the following questions

Question 1

What is an operator?

An operator is a symbol or sign used to specify an operation to be performed in Java

programming.

Question 2

Name the different types of operators.

The different types of operators are Arithmetical, Logical and Relational.

Question 3

Explain the following:

(a) Arithmetical operator

Arithmetic operators are used to perform mathematical operations on its operands.
Operands of arithmetic operators must be of numeric type. A few arithmetic operators
operate upon one operand. They are called Unary Arithmetic operators. Other arithmetic
operators operate upon two operands. They are called Binary Arithmetic operators. As an
example consider the below statement:
int a = 10 + 20;
Here, the addition arithmetic operator, represented by the symbol + will add 10 and 20. So
variable a will be 30.
(b) Relational operator
Relational operators are used to determine the relationship between the operands.
Relational operators compare their operands to check if the operands are equal to ( == ),
not equal to ( != ), less than ( < ), less than equal to ( <= ), greater than ( > ), greater than
equal to ( >= ) each other. The result of an operation involving relation operators is a
boolean value — true or false.
Example:
int a = 8;
int b = 10;
boolean c = a < b;
Here, as a is less than b so the result of a < b is true. Hence, boolean
variable c becomes true.
(c) Logical operator
Logical operators operate on boolean expressions to combine the results of these boolean
expression into a single boolean value.
Example:
int a = 7;
int b = 10;
boolean c = a < b && a % 2 == 0;
Here, the result of first boolean expression a < b is true and the result of second boolean
expression a % 2 is false. The logical AND operator ( && ) combines
these true and false boolean values and gives a resultant boolean value as false. So,
boolean variable c becomes false.
(d) Unary operator
Operators that act on one operand are called as Unary operators. Unary +, unary -, ++, --,
etc. are some unary operators in Java.

(e) New operator

new operator is used to instantiate an object by dynamically allocating memory for it.

(f) Binary operator

Operators that act on two operands are called as Binary operators.

Question 4

What is a Ternary operator? Explain with the help of an example.

condition ? expression 1 : expression 2

Ternary operator evaluates the condition. If the condition is true then result of ternary
operator is the value of expression 1. Otherwise the result is the value of expression 2.
Example:
boolean isLeapYear = true;
int febDays = isLeapYear ? 29 : 28;
Here, the ternary operator checks if the value of boolean variable isLeapYear is true or
false. As it is true, expression 1, which in this example is the value 29, is the result of the
ternary operator. So, int variable febDays becomes 29.

Question 5
Differentiate between the following:

(a) Arithmetical operator and Logical operator

Arithmetical Operator Logical Operator

Arithmetic operators are used to Logical operators operate on boolean expressions to combine the
perform mathematical operations. results of these boolean expression into a single boolean value.

+, -, *, /, etc. are a few examples of

&&, ||, ! are a few examples of Logical Operators
Arithmetic operators.

(b) Binary operator and Ternary operator

Binary operator Ternary operator

Binary operators work on two operands. Ternary operator work on three operands.

+, -, *, /, etc. are a few examples of Binary operators. The conditional operator ? : is a Ternary operator

(c) Logical AND (&&) and Logical OR(||)

Logical AND (&&) Logical OR(||)

It evaluates to true only if both of its operands are

It evaluates to true if one or both of its operands are tru
true.

Example: Example:
int a = 8, b = 13, c = 0; int a = 8, b = 13, c = 0;
if (a > 10 && b > 10) if (a > 10 || b > 10)
c = 10; c = 10;
else else
c = 5; c = 5;
Here, value of c will be 5 as one of the operands is Here, value of c will be 10 as at least one of the operan
false. true.

(d) Prefix operator and Postfix operator

 Prefix Operator Postfix Operator

It works on the principle of CHANGE-THEN-

It works on the principle of USE-THEN-CHANGE.
USE.

It is written before the operand. It is written after the operand.

Example: Example:
int a = 99; int a = 99;
int b = ++a; int b = a++;
After the execution of these two statements, both After the execution of these two statements, a will have
a and b will have the value of 100. value of 100 and b will have the value of 99.
(e) System.out.print( ) and System.out.println( )

System.out.print( ) System.out.println( )

It prints data to the console but the cursor remains at the end It prints data to the console and places the c
of the data in the same line. in the next line.

Next printing takes place from the same line. Next printing takes place from next line.

Question 6

Differentiate between an operator and an expression.

An operator is a symbol or sign used to specify an operation to be performed whereas an

expression is a set of variables, constants and operators i.e. an expression is a combination
of operators and operands.

Question 7

If m=5 and n=2 then what will be the output of m and n after execution that will store in (a) &
(b)?

(a) m -= n;

Answer

m -= n
⇒m=m-n
⇒m=5-2
⇒m=3

(b) n = m + m/n;

Answer

n = m + m/n
⇒n=5+5/2
⇒n=5+2
⇒n=7

Question 8

State the difference between = and ==.

= ==

It is the assignment operator used for assigning a It is the equality operator used to check if a variable is eq
value to a variable. to another variable or literal.

E.g. int a = 10; assigns 10 to variable a. E.g. if (a == 10) checks if variable a is equal to 10 or not.

Question 9

What will be the output for the following program segment?

int a=0,b=10,c=40;
a = --b + c++ +b;
System.out.println(" a = " + a);

Output

a = 58

Explanation

a = --b + c++ + b
⇒ a = 9 + 40 + 9
⇒ a = 58

Question 10
What will be the output of the following?
if x =5

(a) 5* ++x;

Answer

5 * ++x
⇒5*6
⇒ 30

(b) 5* x++;

Answer

5 * x++
⇒5*5
⇒ 25

Question 11

Evaluate the following expressions, if the values of the variables are:

a = 2, b = 3, and c = 9

(a) a - (b++) * (--c);

Answer

a - (b++) * (--c)
⇒2-3*8
⇒2-3*8
⇒ 2 - 24
⇒ -22

(b) a * (++b) % c;

Answer

a * (++b) % c
⇒ a * (++b) % c
⇒ 2 * (4) % 9
⇒8%9
⇒8

Question 12
If a = 5, b = 9, calculate the value of:
a += a++ - ++b + a;

Answer

a += a++ - ++b + a
⇒ a = a + (a++ - ++b + a)
⇒ a = 5 + (5 - 10 + 6)
⇒a=5+1
⇒a=6

Question 13

Give the output of the program snippet.

int a = 10, b =12;

if(a>=10)
a++;
else
++b;
System.out.println(" a = " + a + " and b = " +b);

Output

a = 11 and b = 12

Explanation

The condition if(a>=10) is true so a++ increments a to 11. b remains the same.

Question 14

Rewrite the following using ternary operator.

if(income<=100000)
tax = 0;
else
tax = (0.1*income);

Answer

tax = income <= 100000 ? 0 : (0.1*income);

Question 15

Rewrite the following using ternary operator.

if(p>5000)
d = p*5/100;
else
d = 2*p/100;

Answer

d = p > 5000 ? p * 5 / 100 : 2 * p / 100;

Solutions to Unsolved Java Programs

Question 1
Write a program to find and display the value of the given expressions:
(a) (x + 3) / 6 - (2x + 5) / 3; taking the value of x = 5
public class KboatExpression
{
public static void main(String args[]) {
int x = 5;
double value = ((x + 3) / 6.0) - ((2 * x + 5) / 3.0);
System.out.println("Result = " + value);
}
}

Output

(b) a2 + b2 + c2 / abc; taking the values a=5,b=4,c=3

public class KboatExpression
{
public static void main(String args[]) {
int a = 5, b = 4, c = 3;
double value = (a * a + b * b + c * c) / (double)(a * b * c);
System.out.println("Result = " + value);
}
}

Output
Question 2
A person is paid ₹350 for each day he works and fined ₹30 for each
day he remains absent. Write a program to calculate and display his
monthly income, if he is present for 25 days and remains absent for 5
days.
public class KboatSalary
{
public static void main(String args[]) {
int salary = 25 * 350;
int fine = 5 * 30;
int netSalary = salary - fine;
System.out.println("Monthly Income = " + netSalary);
}
}

Output

Question 3
In a competitive examination, there were 150 questions. One candidate
got 80% correct and the other candidate 72% correct. Write a program
to calculate and display the correct answers each candidate got.
public class KboatCompetitiveExam
{
public static void main(String args[]) {
int totalQuestions = 150;
int c1 = (int)(80 / 100.0 * totalQuestions);
int c2 = (int)(72 / 100.0 * totalQuestions);
System.out.println("Correct Answers of Candidate 1 = " + c1);
System.out.println("Correct Answers of Candidate 2 = " + c2);
}
}

Output
Question 4
Write a program to find and display the percentage difference, when:
(a) a number is updated from 80 to 90
public class KboatPercentIncrease
{
public static void main(String args[]) {
int orgNum = 80;
int newNum = 90;
int inc = newNum - orgNum;
double p = inc / (double)orgNum * 100;
System.out.println("Percentage Difference = " + p + "%");
}
}

Output

(b) a number is updated from 7.5 to 7.2

public class KboatPercentIncrease
{
public static void main(String args[]) {
double orgNum = 7.5;
double newNum = 7.2;
double inc = newNum - orgNum;
double p = inc / orgNum * 100;
System.out.println("Percentage Difference = " + p + "%");
}
}

Output

Question 5
The normal temperature of human body is 98.6°F. Write a program to
convert the temperature into degree Celsius and display the output.
Hint: c / 5 = f - 32 / 9
public class KboatCelsius
{
public static void main(String args[]) {
double f = 98.6;
double c = 5 * (f - 32) / 9.0;
System.out.println("Temperature in Degree Celsius = " + c);
}
}

Output

Question 6
The angles of a quadrilateral are in the ratio 3:4:5:6. Write a program to
find and display all of its angles. [Hint: The sum of angles of a
quadrilateral = 360°]
public class KboatQuadRatio
{
public static void main(String args[]) {
int r1 = 3, r2 = 4, r3 = 5, r4 = 6;
double x = 360 / (double)(r1 + r2 + r3 + r4);
double a = r1 * x;
double b = r2 * x;
double c = r3 * x;
double d = r4 * x;
System.out.println("Angle A = " + a);
System.out.println("Angle B = " + b);
System.out.println("Angle C = " + c);
System.out.println("Angle D = " + d);
}
}