Class 9 Conditional Constructs in Java Mock Test (ICSE)

Topics in Conditional Constructs in Java

• if, if-else and if-else-if
• Nested if
• switch-case with break and default
• Fall through
• Menu-driven programs
• System.exit

Conditional Constructs in Java practice questions with answers

1. Q1Multiple choice·1 mark
   What will be the output of the following nested if code snippet? int a = 5, b = 10; if (a > 0) { if (b < 5) System.out.print("One "); else System.out.print("Two "); } else { System.out.print("Three "); }

   1. (a)Three
   2. (b)One
   3. (c)Two
   4. (d)One Two
   Show answer and step marks

   1. Correct option: (c) Two+1

   Answer: (c)
2. Q2Multiple choice·1 mark
   Which statement, when executed, ends the whole Java program immediately, wherever it appears?

   1. (a)break;
   2. (b)continue;
   3. (c)A nested if statement
   4. (d)System.exit(0);
   Show answer and step marks

   1. Correct option: (d) System.exit(0);+1

   Answer: (d)
3. Q3Short answer·2 marks
   Explain the term 'fall through' in the context of a switch-case statement in Java. Why is a `break` statement typically used to prevent it?
   Show answer and step marks

   1. Definition: Fall through occurs when execution flows into subsequent case blocks without checking if their case constants match, because a break statement is missing.+1
   2. Role of break: A break statement is used to terminate the switch block immediately after a matching case is executed, preventing unintended execution of subsequent cases.+1

   Answer: Fall through: when a matching case has no `break`, execution continues into the statements of the following cases (and `default`) without checking their case values. A `break` ends the switch block as soon as the matching case's statements have run, so the later cases are not executed.
4. Q4Short answer·3 marks
   Study the Java code given below. int age = 15; boolean member = true; if (age ≥ 12) { if (member) { System.out.println("Discount"); } else { System.out.println("Regular"); } } else { System.out.println("Child"); } (a) Name the condition tested by the inner if statement. [1] (b) State the output when age is 10 and member is false. [1] (c) State the output when age is 15 and member is false. [1]
   Show answer and step marks

   1. (a) The inner if tests the condition member, which is true when the value is true.+1
   2. (b) age is 10, so age ≥ 12 is false and the outer else prints Child.+1
   3. (c) age is 15, so the outer if is true; member is false, so the inner else prints Regular.+1

   Answer: (a) member; (b) Child; (c) Regular
5. Q5Long answer·4 marks
   Write a menu-driven program in Java using a $\text{switch-case}$ statement to perform the following operations based on the user's choice: 1. Calculate the area of a circle (Formula: $\pi \times r^2$, take $\pi = 3.142$) 2. Calculate the area of a rectangle (Formula: $\text{length} \times \text{breadth}$) 3. Calculate the area of a square (Formula: $\text{side}^2$) For any invalid choice, display the message "Invalid Choice". Accept all necessary inputs using the $\text{Scanner}$ class.
   Show answer and step marks

   1. Imports $\text{java.util.Scanner}$, declares the class and the $\text{main}$ method, and creates a $\text{Scanner}$ object.+0.5
   2. Displays the menu and reads the user's choice with $\text{nextInt()}$.+0.5
   3. Reads the required dimensions (radius; length and breadth; side) with a $\text{Scanner}$ method such as $\text{nextDouble()}$ or $\text{nextInt()}$.+0.5
   4. Uses $\text{switch(choice)}$ with a $\text{break}$ after each case.+0.5
   5. Case 1: computes and prints the area of the circle as $3.142 \times r \times r$.+0.5
   6. Case 2: computes and prints the area of the rectangle as $\text{length} \times \text{breadth}$.+0.5
   7. Case 3: computes and prints the area of the square as $\text{side} \times \text{side}$.+0.5
   8. The $\text{default}$ case prints "Invalid Choice".+0.5

   Answer: import java.util.Scanner; public class AreaMenu { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("1. Area of a circle"); System.out.println("2. Area of a rectangle"); System.out.println("3. Area of a square"); System.out.print("Enter your choice: "); int choice = sc.nextInt(); switch (choice) { case 1: System.out.print("Enter the radius: "); double r = sc.nextDouble(); System.out.println("Area of the circle = " + (3.142 × r × r)); break; case 2: System.out.print("Enter the length and breadth: "); double l = sc.nextDouble(); double b = sc.nextDouble(); System.out.println("Area of the rectangle = " + (l × b)); break; case 3: System.out.print("Enter the side: "); double s = sc.nextDouble(); System.out.println("Area of the square = " + (s × s)); break; default: System.out.println("Invalid Choice"); } } }
6. Q6Long answer·4 marks
   Write a menu-driven program in Java using a `switch-case` statement to perform the following operations based on the user's choice: 1. Accept an integer and check whether it is even or odd. 2. Accept an integer and check whether it is positive, negative or zero. Display an appropriate error message for any invalid choice.
   Show answer and step marks

   1. Imports `java.util.Scanner`, declares the class and `main` method, and creates a `Scanner` object.+0.5
   2. Displays the menu and reads the user's choice.+0.5
   3. Uses `switch(choice)` with a `break` after each case.+0.5
   4. Case 1: reads an integer and tests `n % 2 == 0` (or `n % 2 ≠ 0` for odd; `n % 2 == 1` is wrong for negative odd numbers).+0.5
   5. Case 1: prints that the number is even when the test is true and odd otherwise.+0.5
   6. Case 2: reads an integer and tests `n > 0` and `n < 0`.+0.5
   7. Case 2: prints positive, negative, or zero for the remaining case.+0.5
   8. The `default` case prints an error message for an invalid choice.+0.5

   Answer: import java.util.Scanner; public class NumberMenu { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("1. Check even or odd"); System.out.println("2. Check positive, negative or zero"); System.out.print("Enter your choice: "); int choice = sc.nextInt(); switch (choice) { case 1: System.out.print("Enter an integer: "); int n = sc.nextInt(); if (n % 2 == 0) System.out.println(n + " is even"); else System.out.println(n + " is odd"); break; case 2: System.out.print("Enter an integer: "); int m = sc.nextInt(); if (m > 0) System.out.println(m + " is positive"); else if (m < 0) System.out.println(m + " is negative"); else System.out.println(m + " is zero"); break; default: System.out.println("Invalid choice! Please enter 1 or 2."); } } }

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