Class 9 Iterative Constructs in Java Mock Test (ICSE)

Topics in Iterative Constructs in Java

• for, while and do-while loops
• Entry- and exit-controlled loops
• break and continue
• Infinite and empty loops
• Number programs using loops

Iterative Constructs in Java practice questions with answers

1. Q1Multiple choice·1 mark
   Consider the following Java code snippet: int p = 1; for (int i = 1; i ≤ 4; i++) { if (i == 2) continue; if (i == 4) break; p = p × i; } System.out.println(p); What will be the output of the above code snippet?

   1. (a)$3$
   2. (b)$12$
   3. (c)$1$
   4. (d)$6$
   Show answer and step marks

   1. Correct option: (a) $3$+1

   Answer: (a)
2. Q2Assertion and reason·1 mark
   Assertion (A): A break statement exits the loop in which it is written. Reason (R): The continue statement is used to end the entire loop permanently.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
   3. (c)Assertion (A) is true but Reason (R) is false.
   4. (d)Assertion (A) is false but Reason (R) is true.
   Show answer and step marks

   1. Correct option: (c) Assertion (A) is true but Reason (R) is false.+1

   Answer: (c)
3. Q3Multiple choice·1 mark
   Consider the following Java code snippet: int n = 456; int c = 0; while(n > 0) { c++; n = n / 10; } System.out.println(c); What will be the output of the above snippet?

   1. (a)2
   2. (b)3
   3. (c)4
   4. (d)456
   Show answer and step marks

   1. Correct option: (b) 3+1

   Answer: (b)
4. Q4Short answer·3 marks
   Study the Java code given below. int i; for (i = 1; i ≤ 5; i++); { System.out.println("Done"); } (a) State the output of the program. [1] (b) Explain why the block runs only once although the for loop is meant to run five times. [1] (c) Explain why the loop would never end if the update i++ were removed from the for statement. [1]
   Show answer and step marks

   1. (a) The semicolon after the for statement makes its body empty, so the block runs once and Done is printed once.+1
   2. (b) The semicolon ends the for statement with an empty body, so the loop only updates i and the block is a separate statement executed once.+1
   3. (c) Without i++, i stays at 1, so i ≤ 5 is always true and the empty body never changes i, so the loop never ends.+1

   Answer: (a) Done is printed once; (b) the semicolon gives the for loop an empty body, so the block is outside the loop; (c) i never changes, so the condition i ≤ 5 stays true forever.
5. Q5Short answer·3 marks
   At a water treatment plant, the laboratory uses the following Java program to print a reversed four-digit sample code on the audit sheet: int n = 4072; int rev = 0; while (n ≠ 0) { rev = rev × 10 + n % 10; n = n / 10; } System.out.println(rev); (a) State the value printed by the program. [1] (b) Explain why the statement n = n / 10 removes the last digit of n from the number. [2]
   Show answer and step marks

   1. (a) Output: 2704+1
   2. (b) With int operands, n / 10 performs integer division and discards the fractional part, so 4072 / 10 gives 407.+1
   3. (b) The units digit 2 is lost because the remainder left after division by 10 is dropped, and the loop then works on the remaining digits.+1

   Answer: (a) 2704. (b) Integer division of n by 10 discards the remainder, so the units digit is dropped (4072 becomes 407).
6. Q6Long answer·4 marks
   Consider the following Java code segment designed to print numbers from $1$ to $5$: int i = 1; while (i ≤ 5); { System.out.println(i); i++; } (a) Identify the logical error in the code that creates an empty loop and an infinite loop, and explain why it occurs. [2 marks] (b) Rewrite the corrected Java code snippet so that it executes properly and prints the numbers from $1$ to $5$. [2 marks]
   Show answer and step marks

   1. Error: a semicolon (;) is placed immediately after the while condition.+1
   2. The semicolon is an empty statement that becomes the loop body, so i is never incremented, i ≤ 5 stays true and the loop runs forever.+1
   3. Correction: remove the semicolon so the block becomes the loop body.+1
   4. Correct code: int i = 1; while (i ≤ 5) { System.out.println(i); i++; }+1

   Answer: (a) The semicolon after while (i ≤ 5) makes an empty loop body, so i stays 1 and the loop never ends. (b) int i = 1; while (i ≤ 5) { System.out.println(i); i++; }

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