If statement in Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the number is positive.

Java

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

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

A>

B<

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '>' to check positivity.

Using '<' which checks for negative numbers.

The condition number > 0 checks if the number is positive.

2fill in blank

medium

Complete the code to print "Even number" if the number is even.

Java

if (number [1] 2 == 0) {
    System.out.println("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 '+' which are not correct here.

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

3fill in blank

hard

Fix the error in the if statement condition to check if age is at least 18.

Java

if (age [1] 18) {
    System.out.println("Adult");
}

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

A>=

B<=

C<

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' or '<=' which check for younger ages.

Using '==' which only checks exactly 18.

The condition age >= 18 checks if age is 18 or older.

4fill in blank

hard

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

Java

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 '<' instead of '<=' for the upper bound.

Using '>' instead of '>=' for the lower bound.

The condition number >= 10 && number <= 20 checks if the number is between 10 and 20 including both ends.

5fill in blank

hard

Fill all three blanks to print the grade based on score: A if score >= 90, B if score >= 80, else C.

Java

if (score [1] 90) {
    System.out.println("Grade A");
} else if (score [2] 80) {
    System.out.println("Grade B");
} else {
    System.out.println("Grade [3]");
}

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

A>=

CC

DB

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>=' in conditions.

Printing wrong grade letters in else block.

The first condition checks if score is 90 or more for grade A. The second checks if score is 80 or more for grade B. Otherwise, grade C is printed.

Practice

1. What does an if statement do in Java?

easy

A. It stores data in a variable.

B. It repeats code multiple times.

C. It creates a new class.

D. It runs code only if a condition is true.

Solution

1. Step 1: Understand the purpose of an if statement

   An if statement checks a condition and decides whether to run some code based on that condition.

2. Step 2: Match the description to the options

   It runs code only if a condition is true. correctly says it runs code only if the condition is true, which matches the if statement's behavior.

3. Final Answer:

   It runs code only if a condition is true. -> Option D

4. Quick Check:

   If statement = runs code if true [OK]

Hint: If checks true condition to run code [OK]

Common Mistakes:

• Confusing if with loops
• Thinking if stores data
• Mixing if with class creation

2. Which of these is the correct syntax for an if statement in Java?

easy

A. if (condition) System.out.println("Yes");

B. if condition { System.out.println("Yes"); }

C. if condition: System.out.println("Yes");

D. if (condition) then { System.out.println("Yes"); }

Solution

1. Step 1: Recall Java if statement syntax

   Java requires parentheses around the condition and braces are optional if only one statement follows.

2. Step 2: Check each option

   if (condition) System.out.println("Yes"); uses parentheses and a single statement without braces, which is valid syntax.

3. Final Answer:

   if (condition) System.out.println("Yes"); -> Option A

4. Quick Check:

   Parentheses needed around condition [OK]

Hint: Use parentheses around condition in if [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using colons instead of braces
• Adding 'then' keyword

3. What will be the output of this code?

int x = 10;
if (x > 5) {
  System.out.println("Big number");
} else {
  System.out.println("Small number");
}

medium

A. Small number

B. Big number

C. No output

D. Syntax error

Solution

1. Step 1: Evaluate the condition x > 5

   Since x is 10, the condition 10 > 5 is true.

2. Step 2: Determine which block runs

   The if block runs and prints "Big number" because the condition is true.

3. Final Answer:

   Big number -> Option B

4. Quick Check:

   10 > 5 is true, prints "Big number" [OK]

Hint: Check if condition true to pick output [OK]

Common Mistakes:

• Choosing else output when condition is true
• Thinking no output if condition true
• Confusing syntax with output

4. Find the error in this code:

int num = 7;
if num > 5 {
  System.out.println("Greater");
}

medium

A. Braces not allowed in if

B. Missing semicolon after if

C. Missing parentheses around condition

D. Wrong variable name

Solution

1. Step 1: Check if statement syntax

   Java requires parentheses around the condition in an if statement.

2. Step 2: Identify the missing parentheses

   The code has if num > 5 without parentheses, which causes a syntax error.

3. Final Answer:

   Missing parentheses around condition -> Option C

4. Quick Check:

   If condition must be in parentheses [OK]

Hint: Always put condition in parentheses [OK]

Common Mistakes:

• Forgetting parentheses around condition
• Adding semicolon after if line
• Misnaming variables

5. You want to print "Even" if a number is even and "Odd" if it is odd. Which code correctly uses an if statement to do this?

int n = 4;
// Your code here

hard

A. if (n % 2 == 0) {
System.out.println("Even");
} else {
System.out.println("Odd");
}

B. if (n / 2 == 0) {
System.out.println("Even");
} else {
System.out.println("Odd");
}

C. if (n % 2 = 0) {
System.out.println("Even");
} else {
System.out.println("Odd");
}

D. if (n % 2 != 0) {
System.out.println("Even");
} else {
System.out.println("Odd");
}

Solution

1. Step 1: Understand how to check even numbers

   A number is even if dividing by 2 leaves remainder 0, so use n % 2 == 0.

2. Step 2: Check each option's condition

   if (n % 2 == 0) { System.out.println("Even"); } else { System.out.println("Odd"); } correctly uses n % 2 == 0 to check evenness and prints "Even" or "Odd" accordingly.

3. Final Answer:

   if (n % 2 == 0) { System.out.println("Even"); } else { System.out.println("Odd"); } -> Option A

4. Quick Check:

   Use modulus == 0 for even check [OK]

Hint: Use n % 2 == 0 to check even numbers [OK]

Common Mistakes:

• Using assignment = instead of comparison ==
• Checking division instead of remainder
• Reversing even and odd conditions