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Chapter 1 - Unit 7

Conditional Statements in Java

Class 10 - APC Understanding Computer Applications with BlueJ


State whether the following statements are 'True' or 'False'

Question 1

if statement is also called as a conditional statement.
True

Question 2

A conditional statement is essentially formed by using relational operators.
True

Question 3

An if-else construct accomplishes 'fall through'.
False

Question 4

In a switch case, when the switch value does not match with any case then the execution transfers to the default case.
True

Question 5

The break statement may not be used in a switch statement.
False

Tick the correct answer

Question 1

If m, n, p are the three integers, then which of the following holds true, if(m==n)&&(n!=p)?

  1. 'm' and 'n' are equal ✓
  2. 'n' and 'p' are equal
  3. 'm' and 'p' are equal
  4. none

Question 2

A compound statement can be stated as

  1. p=in.nextInt();
    q=in.nextInt();
  2. m=++a;
    n=--b;
  3. if(a>b)
    {a++;b--;} ✓
  4. none

Question 3

If((p>q)&&(q>r)) then

  1. q is the smallest number
  2. q is the greatest number
  3. p is the greatest number ✓
  4. none

(where p, q and r are three integer numbers)

Question 4

if(a<b)
c=a;
else
c=b;

It can be written as:

  1. c= (b<a)?a:b;
  2. c= (a!=b)?a:b;
  3. c= (a<b)?b:a;
  4. none ✓

Question 5

If(a<b && a<c)

  1. a is the greatest number
  2. a is the smallest number ✓
  3. b is the greatest number
  4. none

(where a, b and c are three integer numbers)

Write the Java expressions for the following

Question 1

ab+cd3\sqrt[3]{ab + cd}

Java expression
Math.cbrt(a * b + c * d)

Question 2

p3+q412rp^3 + q^4 - \dfrac{1}{2}r

Java expression
p * p * p + q * q * q * q - 1 / 2 * r

Question 3

(b+b24ac)2a\dfrac{(-b + \sqrt{b^2 - 4ac})}{2a}

Java expression
(-b + Math.sqrt(b * b - 4 * a * c)) / 2 * a

Question 4

0.052y3xy\dfrac{0.05 - 2y^3}{x - y}

Java expression
(0.05 - 2 * y * y * y) / (x - y)

Question 5

mn+m+n3\sqrt{mn} + \sqrt[3]{m + n}

Java expression
Math.sqrt(m * n) + Math.cbrt(m + n)

Question 6

34(a+b)25ab\dfrac{3}{4}(a + b) - \dfrac{2}{5}ab

Java expression
3 / 4 * (a + b) - 2 / 5 * a * b

Question 7

38(b2+c3)\dfrac{3}{8}\sqrt{(b^2 + c^3)}

Java expression
3 / 8 * Math.sqrt(b * b + c * c * c)

Question 8

a3+b2c3\sqrt[3]a + b^2 - \sqrt[3]c

Java expression
Math.cbrt(a) + b * b - Math.cbrt(c)

Question 9

a+b2+c33\dfrac{\sqrt{a + b^2 + c^3}}{3}

Java expression
Math.sqrt(a + b * b + c * c * c) / 3

Question 10

3x+x2(a+b)\dfrac{\sqrt{3x + x^2}}{(a + b)}

Java expression
Math.sqrt(3 * x + x * x) / (a + b)

Predict the output

Question 1

int m=3,n=5,p=4;
if(m==n && n!=p)
{
System.out.println(m*n);
System.out.println(n%p);
}
if((m!=n) || (n==p))
{
System.out.println(m+n);
System.out.println(m-n);
}
Output
8
-2
Explanation

The first if condition — if(m==n && n!=p), tests false as m is not equal to n. The second if condition — if((m!=n) || (n==p)) tests true so the statements inside its code block are executed printing 8 and -2 to the console.

Question 2

int a=1,b=2,c=3;
switch(p)
{
case 1: a++;
case 2: ++b;
break;
case 3: c--;
}
System.out.println(a + ","
+ b + "," +c);

(i) p = 1

Output
2,3,3
Explanation

When p is 1, case 1 is matched. a++ increments value of a to 2. As there is no break statement, fall through to case 2 happens. ++b increments b to 3. break statement in case 2 transfers program control to println statement and we get the output as 2,3,3.

(ii) p = 3

Output
1,2,2
Explanation

When p is 3, case 3 is matched. c-- decrements c to 2. Program control moves to the println statement and we get the output as 1,2,2.

Convert the following constructs as directed

Question 1

switch case construct into if-else-if :

switch (n)
{
case 1: 
s=a+b; 
System.out.println("Sum="+s);
break; 
case 2: 
d=a-b; 
System.out.println("Difference="+d);
break: 
case 3: 
p=a*b; 
System.out.println("Product="+p);
break; 
default: 
System.out.println("Wrong Choice!");
}
Answer
if (n == 1) {
    s = a + b;
    System.out.println("Sum="+s);
}
else if (n == 2) {
    d = a - b; 
    System.out.println("Difference="+d);
}
else if (n == 3) {
    p = a * b; 
    System.out.println("Product="+p);
}
else {
    System.out.println("Wrong Choice!");
}

Question 2

if-else-if construct into switch case:

if(var==1)
System.out.println("Distinction"); 
else if(var==2)
System.out.println("First Division"); 
else if(var==3)
System.out.println("Second Division"); 
else
System.out.println("invalid"); 
Answer
switch (var) {
    case 1:
    System.out.println("Distinction");
    break;
    case 2:
    System.out.println("First Division");
    break;
    case 3:
    System.out.println("Second Division");
    break;
    default:
    System.out.println("invalid");
}

Answer the following questions

Question 1

What is meant by 'conditional' statement? Explain.

Answer

The order in which the statements of a program are executed is known as control flow. By default, the statements of a program are executed from top to bottom in order in which they are written. But most of the times our programs require to alter this top to bottom control flow based on some condition. The statements that help us to alter the control flow of the program are known as conditional statements.

Question 2

What is the significance of System.exit(0)?

Answer

System.exit(0) terminates the execution of the program by stopping the Java Virtual Machine which is executing the program. It is generally used when due to some reason it is not possible to continue with the execution of the program. For example, if I am writing a program to find the square root of a number and the user enters a negative number then it is not possible for me to find the square root of a negative number. In such situations, I can use System.exit(0) to terminate the program. The example program to find the square root of a number is given below:

import java.util.Scanner;
public class SquareRootExample {
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter the number: ");
        int n = in.nextInt();
        if (n < 0) {
            System.out.println("Cannot find square root of a negative number");
            System.exit(0);
        }
        double sqrt = Math.sqrt(n);
        System.out.println("Square root of " + n + " = " + sqrt);
    }
}

Question 3

Is it necessary to include 'default' case in a switch statement? Justify.

Answer

'default' case is optional in a switch statement. It is included to takecare of the situation when none of the case values are equal to the expression of switch statement. Consider the below example:

int number = 4;
    
switch(number) {
    
    case 0:
        System.out.println("Value of number is zero");
        break;
        
    case 1:
        System.out.println("Value of number is one");
        break;
        
    case 2:
        System.out.println("Value of number is two");
        break;
        
    default:
        System.out.println("Value of number is greater than two");
        break;
        
}

Here, value of number is 4 so case 0, case 1 and case 2 are not equal to number. Hence SOPLN of default case will get executed printing "Value of number is greater than two" to the console. If we don't include default case in this example then also the program is syntactically correct but we will not get any output when value of number is anything other than 0, 1 or 2.

Question 4

What will happen if 'break' statement is not used in a switch case? Explain.

Answer

Use of break statement in a switch case statement is optional. Omitting break statement will lead to fall through where program execution continues into the next case and onwards till end of switch statement is reached.

Question 5

When does 'Fall through' occur in a switch statement? Explain.

Answer

break statement at the end of case is optional. Omitting break leads to program execution continuing into the next case and onwards till a break statement is encountered or end of switch is reached. This is termed as Fall Through in switch case statement.

Question 6

What is a compound statement? Give an example.

Answer

Two or more statements can be grouped together by enclosing them between opening and closing curly braces. Such a group of statements is called a compound statement.

if (a < b) {
            
    /*
    * All statements within this set of braces 
    * form the compound statement
    */

    System.out.println("a is less than b");
    a = 10;
    b = 20;
    System.out.println("The value of a is " + a);
    System.out.println("The value of b is " + b);
            
}

Question 7

Explain if-else-if construct with an example.

Answer

if-else-if construct is used to test multiple conditions and then take a decision. It provides multiple branching of control. Below is an example of if-else-if:

if (marks < 35)
    System.out.println("Fail");
else if (marks < 60)
    System.out.println("C grade");
else if (marks < 80)
    System.out.println("B grade");
else if (marks < 95)
    System.out.println("A grade");
else
    System.out.println("A+ grade");

Question 8

Give two differences between the switch statement and the if-else statement.

Answer
switchif-else
switch can only test if the expression is equal to any of its case constantsif-else can test for any boolean expression like less than, greater than, equal to, not equal to, etc.
It is a multiple branching flow of control statementIt is a bi-directional flow of control statement

Solutions to Unsolved Java Programs

Question 1

Write a program to input three numbers (positive or negative). If they are unequal then display the greatest number otherwise, display they are equal. The program also displays whether the numbers entered by the user are 'All positive', 'All negative' or 'Mixed numbers'.
Sample Input: 56, -15, 12
Sample Output:
The greatest number is 56
Entered numbers are mixed numbers.

import java.util.Scanner;

public class KboatNumberAnalysis
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter first number: ");
        int a = in.nextInt();
        
        System.out.print("Enter second number: ");
        int b = in.nextInt();
        
        System.out.print("Enter third number: ");
        int c = in.nextInt();
        
        int greatestNumber = a;
        
        if ((a == b) && (b == c)) {
            System.out.println("Entered numbers are equal.");
        }
        else {
            
            if (b > greatestNumber) {
                greatestNumber = b;
            }
            
            if (c > greatestNumber) {
                greatestNumber = c;
            }
            
            System.out.println("The greatest number is " + greatestNumber);
            
            if ((a >= 0) && (b >= 0) && (c >= 0)) {
                System.out.println("Entered numbers are all positive numbers.");
            }
            else if((a < 0) && (b < 0) && (c < 0)) {
                System.out.println("Entered numbers are all negative numbers.");
            }
            else {
                System.out.println("Entered numbers are mixed numbers.");
            }
        }
    }
}
Output
BlueJ output of KboatNumberAnalysis.java

Question 2

A triangle is said to be an 'Equable Triangle', if the area of the triangle is equal to its perimeter. Write a program to enter three sides of a triangle. Check and print whether the triangle is equable or not.
For example, a right angled triangle with sides 5, 12 and 13 has its area and perimeter both equal to 30.

import java.util.Scanner;

public class KboatEquableTriangle
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.println("Please enter the 3 sides of the triangle.");
        
        System.out.print("Enter the first side: ");
        double a = in.nextDouble();
        
        System.out.print("Enter the second side: ");
        double b = in.nextDouble();
        
        System.out.print("Enter the third side: ");
        double c = in.nextDouble();
        
        double p = a + b + c;
        double s = p / 2;
        double area = Math.sqrt(s * (s - a) * (s - b) * (s - c));
        
        if (area == p)
            System.out.println("Entered triangle is equable.");
        else 
            System.out.println("Entered triangle is not equable.");
    }
}
Output
BlueJ output of KboatEquableTriangle.java

Question 3

A special two-digit number is such that when the sum of its digits is added to the product of its digits, the result is equal to the original two-digit number.
Example: Consider the number 59.
Sum of digits = 5 + 9 = 14
Product of digits = 5 * 9 = 45
Total of the sum of digits and product of digits = 14 + 45 = 59
Write a program to accept a two-digit number. Add the sum of its digits to the product of its digits. If the value is equal to the number input, display the message "Special 2 - digit number" otherwise, display the message "Not a special two-digit number".

import java.util.Scanner;

public class KboatSpecialNumber
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter a 2 digit number: ");
        int orgNum = in.nextInt();
        
        if (orgNum < 10 || orgNum > 99) {
            System.out.println("Invalid input. Entered number is not a 2 digit number");
            System.exit(0);
        }
        
        int num = orgNum;
        
        int digit1 = num % 10;
        int digit2 = num / 10;
        num /= 10;
        
        int digitSum = digit1 + digit2;
        int digitProduct = digit1 * digit2;
        int grandSum = digitSum + digitProduct;
        
        if (grandSum == orgNum)
            System.out.println("Special 2-digit number");
        else
            System.out.println("Not a special 2-digit number");
            
    }
}
Output
BlueJ output of KboatSpecialNumber.java

Question 4

The standard form of quadratic equation is given by: ax2 + bx + c = 0, where d = b2 - 4ac, is known as discriminant that determines the nature of the roots of the equation as:

ConditionNature
if d >= 0Roots are real
if d < 0Roots are imaginary

Write a program to determine the nature and the roots of a quadratic equation, taking a, b, c as input. If d = b2 - 4ac is greater than or equal to zero, then display 'Roots are real', otherwise display 'Roots are imaginary'. The roots are determined by the formula as:
r1 = (-b + √(b2 - 4ac)) / 2a , r2 = (-b - √(b2 - 4ac)) / 2a

import java.util.Scanner;

public class KboatQuadEqRoots
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter a: ");
        int a = in.nextInt();
        
        System.out.print("Enter b: ");
        int b = in.nextInt();
        
        System.out.print("Enter c: ");
        int c = in.nextInt();
        
        double d = Math.pow(b, 2) - (4 * a * c);
        
        if (d >= 0) {
            System.out.println("Roots are real.");
            double r1 = (-b + Math.sqrt(d)) / (2 * a);
            double r2 = (-b - Math.sqrt(d)) / (2 * a);
        
            System.out.println("Roots of the equation are:");
            System.out.println("r1=" + r1 + ", r2=" + r2);
        }
        else {
            System.out.println("Roots are imaginary.");
        }
            
        
    }
}
Output
BlueJ output of KboatQuadEqRoots.java
BlueJ output of KboatQuadEqRoots.java

Question 5

An air-conditioned bus charges fare from the passengers based on the distance travelled as per the tariff given below:

Distance TravelledFare
Up to 10 kmFixed charge ₹80
11 km to 20 km₹6/km
21 km to 30 km₹5/km
31 km and above₹4/km

Design a program to input distance travelled by the passenger. Calculate and display the fare to be paid.

import java.util.Scanner;

public class KboatBusFare
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter distance travelled: ");
        int dist = in.nextInt();
        
        int fare = 0;
        
        if (dist <= 0)
            fare = 0;
        else if (dist <= 10)
            fare = 80;
        else if (dist <= 20)
            fare = 80 + (dist - 10) * 6;
        else if (dist <= 30)
            fare = 80 + 60 + (dist - 20) * 5;
        else if (dist > 30)
            fare = 80 + 60 + 50 + (dist - 30) * 4;
            
        System.out.println("Fare = " + fare);
    }
}
Output
BlueJ output of KboatBusFare.java

Question 6

An ICSE school displays a notice on the school notice board regarding admission in Class XI for choosing stream according to marks obtained in English, Maths and Science in Class 10 Council Examination.

Marks obtained in different subjectsStream
Eng, Maths and Science >= 80%Pure Science
Eng and Science >= 80%, Maths >= 60%Bio. Science
Eng, Maths and Science >= 60%Commerce

Print the appropriate stream allotted to a candidate. Write a program to accept marks in English, Maths and Science from the console.

import java.util.Scanner;

public class KboatAdmission
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter marks in English: ");
        int eng = in.nextInt();
        
        System.out.print("Enter marks in Maths: ");
        int maths = in.nextInt();
        
        System.out.print("Enter marks in Science: ");
        int sci = in.nextInt();
        
        if (eng >= 80 && sci >= 80 && maths >= 80) 
            System.out.println("Pure Science");
        else if (eng >= 80 && sci >= 80 && maths >= 60)
            System.out.println("Bio. Science");
        else if (eng >= 60 && sci >= 60 && maths >= 60)
            System.out.println("Commerce");
        else
            System.out.println("Cannot allot stream");
    }
}
Output
BlueJ output of KboatAdmission.java

Question 7

A bank announces new rates for Term Deposit Schemes for their customers and Senior Citizens as given below:

TermRate of Interest (General)Rate of Interest (Senior Citizen)
Up to 1 year7.5%8.0%
Up to 2 years8.5%9.0%
Up to 3 years9.5%10.0%
More than 3 years10.0%11.0%

The 'senior citizen' rates are applicable to the customers whose age is 60 years or more. Write a program to accept the sum (p) in term deposit scheme, age of the customer and the term. The program displays the information in the following format:

Amount DepositedTermAgeInterest earnedAmount Paid
xxxxxxxxxxxxxxx
import java.util.Scanner;

public class KboatBankDeposit
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter sum: ");
        double sum = in.nextDouble();
        
        System.out.print("Enter age: ");
        int age = in.nextInt();
        
        System.out.print("Enter term: ");
        double term = in.nextDouble();
        
        double si = 0.0;
        
        if (term <= 1 && age < 60)
            si = (sum * 7.5 * term) / 100;
        else if (term <= 1 && age >= 60)
            si = (sum * 8.0 * term) / 100;
        else if (term <= 2 && age < 60)
            si = (sum * 8.5 * term) / 100;
        else if (term <= 2 && age >= 60)
            si = (sum * 9.0 * term) / 100;
        else if (term <= 3 && age < 60)
            si = (sum * 9.5 * term) / 100;
        else if (term <= 3 && age >= 60)
            si = (sum * 10.0 * term) / 100;
        else if (term > 3 && age < 60)
            si = (sum * 10.0 * term) / 100;
        else if (term > 3 && age >= 60)
            si = (sum * 11.0 * term) / 100;
            
        double amt = sum + si;
        
        System.out.println("Amount Deposited: " +  sum);
        System.out.println("Term: " +  term);
        System.out.println("Age: " +  age);
        System.out.println("Interest Earned: " +  si);
        System.out.println("Amount Paid: " +  amt);
    }
}
Output
BlueJ output of KboatBankDeposit.java

Question 8

A courier company charges differently for 'Ordinary' booking and 'Express' booking based on the weight of the parcel as per the tariff given below:

Weight of parcelOrdinary bookingExpress booking
Up to 100 gm₹80₹100
101 to 500 gm₹150₹200
501 gm to 1000 gm₹210₹250
More than 1000 gm₹250₹300

Write a program to input weight of a parcel and type of booking (`O' for ordinary and 'E' for express). Calculate and print the charges accordingly.

import java.util.Scanner;

public class KboatCourierCompany
{
    public static void main(String args[]) {
        
        Scanner in = new Scanner(System.in);
        
        System.out.print("Enter weight of parcel: ");
        double wt = in.nextDouble();
        
        System.out.print("Enter type of booking: ");
        char type = in.next().charAt(0);
        
        double charge = 0;
        
        if (wt <= 0)
            charge = 0;
        else if (wt <= 100 && type == 'O')
            charge = 80;
        else if (wt <= 100 && type == 'E')
            charge = 100;
        else if (wt <= 500 && type == 'O')
            charge = 150;
        else if (wt <= 500 && type == 'E')
            charge = 200;
        else if (wt <= 1000 && type == 'O')
            charge = 210;
        else if (wt <= 1000 && type == 'E')
            charge = 250;
        else if (wt > 1000 && type == 'O')
            charge = 250;
        else if (wt > 1000 && type == 'E')
            charge = 300;
            
        System.out.println("Parcel charges = " + charge);
    }
}
Output
BlueJ output of KboatCourierCompany.java

Video Explanations

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