Nested if statements in Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a number is positive.

Java

int number = 10;
if ([1] > 0) {
    System.out.println("Positive number");
}

Drag options to blanks, or click blank then click option'

Anum

Bcount

Cvalue

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not declared.

Forgetting to compare the variable to 0.

The variable number holds the value to check. Using number in the if condition correctly tests if it is positive.

2fill in blank

medium

Complete the code to check if a number is positive and even.

Java

int number = 8;
if (number > 0) {
    if (number [1] 2 == 0) {
        System.out.println("Positive even number");
    }
}

Drag options to blanks, or click blank then click option'

A%

B/

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using division instead of modulus.

Using multiplication or addition operators incorrectly.

The modulus operator % checks the remainder. If number % 2 == 0, the number is even.

3fill in blank

hard

Fix the error in the nested if statement to check if a number is positive and less than 100.

Java

int number = 50;
if (number > 0) {
    if (number [1] 100) {
        System.out.println("Number is positive and less than 100");
    }
}

Drag options to blanks, or click blank then click option'

A<

B>=

C==

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than instead of less than.

Using equality operator which only checks if number equals 100.

The condition should check if number is less than 100, so the operator < is correct.

4fill in blank

hard

Fill both blanks to check if a number is between 10 and 20 (inclusive).

Java

int number = 15;
if (number [1] 10 && number [2] 20) {
    System.out.println("Number is between 10 and 20");
}

Drag options to blanks, or click blank then click option'

A>=

B<

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using strict greater than or less than which excludes boundaries.

Mixing up the order of operators.

The number should be greater than or equal to 10 and less than or equal to 20, so use >= and <=.

5fill in blank

hard

Fill both blanks to print messages based on nested if conditions for age and score.

Java

int age = 20;
int score = 85;
if (age [1] 18) {
    if (score [2] 80) {
        System.out.println("Adult with high score");
    } else {
        System.out.println("Adult with low score");
    }
} else {
    System.out.println("Not an adult");
}

Drag options to blanks, or click blank then click option'

A>=

B>

C<=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using > instead of >= for age.

Using <= instead of > for score.

The first condition checks if age is at least 18 (>=), the second if score is greater than 80 (>), and the else covers the rest.

Practice

1. What does a nested if statement mean in Java?

easy

A. An if statement without any condition

B. An if statement with multiple conditions joined by ||

C. An if statement inside another if statement

D. An if statement that runs only once

Solution

1. Step 1: Understand the meaning of nested if

   A nested if means placing one if statement inside another to check conditions step-by-step.

2. Step 2: Compare options

   Only An if statement inside another if statement describes an if inside another if. Others describe different concepts.

3. Final Answer:

   An if statement inside another if statement -> Option C

4. Quick Check:

   Nested if = if inside if [OK]

Hint: Look for 'if inside if' meaning nested [OK]

Common Mistakes:

• Confusing nested if with multiple conditions in one if
• Thinking nested if runs only once
• Ignoring the inner if statement

2. Which of the following is the correct syntax for a nested if statement in Java?

easy

A. if (x > 0) if y > 0 { System.out.println("Both positive"); }

B. if (x > 0) { if (y > 0) { System.out.println("Both positive"); } }

C. if x > 0 { if y > 0 { System.out.println("Both positive"); } }

D. if (x > 0) { if (y > 0) System.out.println("Both positive") }

Solution

1. Step 1: Check Java syntax rules for if

   Java requires parentheses around conditions and braces for blocks.

2. Step 2: Validate each option

   if (x > 0) { if (y > 0) { System.out.println("Both positive"); } } uses correct parentheses and braces. if (x > 0) if y > 0 { System.out.println("Both positive"); } misses parentheses around y > 0. if x > 0 { if y > 0 { System.out.println("Both positive"); } } misses parentheses and braces. if (x > 0) { if (y > 0) System.out.println("Both positive") } misses semicolon after println.

3. Final Answer:

   if (x > 0) { if (y > 0) { System.out.println("Both positive"); } } -> Option B

4. Quick Check:

   Correct syntax = if (x > 0) { if (y > 0) { System.out.println("Both positive"); } } [OK]

Hint: Remember: conditions need parentheses, blocks need braces [OK]

Common Mistakes:

• Omitting parentheses around conditions
• Forgetting braces for nested blocks
• Missing semicolons after statements

3. What will be the output of this code?

int a = 5;
int b = 10;
if (a > 0) {
  if (b < 5) {
    System.out.println("Inside inner if");
  } else {
    System.out.println("Inside else of inner if");
  }
} else {
  System.out.println("Inside outer else");
}

medium

A. Inside else of inner if

B. Inside outer else

C. Inside inner if

D. No output

Solution

1. Step 1: Evaluate outer if condition

   a = 5, so a > 0 is true, enter outer if block.

2. Step 2: Evaluate inner if condition

   b = 10, b < 5 is false, so else block of inner if runs.

3. Final Answer:

   Inside else of inner if -> Option A

4. Quick Check:

   Outer if true, inner if false -> inner else [OK]

Hint: Check outer if first, then inner if conditions [OK]

Common Mistakes:

• Ignoring the else block of inner if
• Confusing outer else with inner else
• Assuming no output if inner if false

4. Find the error in this nested if code:

int x = 10;
if (x > 5)
  if (x < 20)
    System.out.println("x is between 5 and 20");
  else
    System.out.println("x is 5 or less");

medium

A. Missing braces causing else to pair with wrong if

B. Incorrect condition syntax

C. Missing semicolon after println

D. Variable x not declared

Solution

1. Step 1: Analyze if-else pairing without braces

   Without braces, else pairs with nearest if, here inner if.

2. Step 2: Understand the logic error

   Else prints "x is 5 or less" only if x >= 20, which is wrong logically.

3. Final Answer:

   Missing braces causing else to pair with wrong if -> Option A

4. Quick Check:

   Braces fix else pairing [OK]

Hint: Use braces to avoid else pairing mistakes [OK]

Common Mistakes:

• Assuming else pairs with outer if
• Ignoring braces importance
• Thinking syntax error instead of logic error

5. You want to write a nested if to check if a number is positive and even. Which code correctly does this?

hard

A. if (num > 0) { if (num % 2 = 0) { System.out.println("Positive even"); } }

B. if (num > 0 && num % 2 == 0) System.out.println("Positive even");

C. if (num > 0) if (num / 2 == 0) System.out.println("Positive even");

D. if (num > 0) { if (num % 2 == 0) { System.out.println("Positive even"); } }

Solution

1. Step 1: Check condition for positive number

   First if checks if num > 0, correct for positive check.

2. Step 2: Check condition for even number inside first if

   Inner if uses num % 2 == 0, correct for even check.

3. Final Answer:

   if (num > 0) { if (num % 2 == 0) { System.out.println("Positive even"); } } -> Option D

4. Quick Check:

   Nested if with correct conditions = if (num > 0) { if (num % 2 == 0) { System.out.println("Positive even"); } } [OK]

Hint: Use % 2 == 0 to check even inside positive check [OK]

Common Mistakes:

• Using single = instead of == in condition
• Using division instead of modulo for even check
• Combining conditions without nesting