Ternary operator in Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign the smaller of two numbers to the variable min using the ternary operator.

Java

int a = 10;
int b = 20;
int min = (a < b) ? [1] : b;

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

Ab

Ba

C10

D20

Attempts:

3 left

💡 Hint

Common Mistakes

Using b instead of a for the true case.

Confusing the order of values in the ternary operator.

The ternary operator checks if a < b. If true, it assigns a to min, otherwise b.

2fill in blank

medium

Complete the code to assign "Even" or "Odd" to the variable result based on whether num is even or odd.

Java

int num = 7;
String result = (num % 2 == 0) ? [1] : "Odd";

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

A"Even"

B"Odd"

Cnum

D"Number"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the true and false values.

Using the variable num instead of string literals.

The ternary operator checks if num % 2 == 0. If true, result is assigned "Even", else "Odd".

3fill in blank

hard

Fix the error in the ternary expression to correctly assign the absolute value of number to absValue.

Java

int number = -5;
int absValue = (number >= 0) ? number : [1];

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

A0

Bnumber

C-number

Dnumber * -1

Attempts:

3 left

💡 Hint

Common Mistakes

Using number instead of its negation for negative values.

Using number * -1 which is correct but less common than -number.

The ternary operator assigns number if it is non-negative; otherwise, it assigns -number to get the absolute value.

4fill in blank

hard

Fill both blanks to create a ternary expression that assigns "Pass" if score is 50 or more, otherwise "Fail".

Java

int score = 65;
String grade = (score [1] 50) ? [2] : "Fail";

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

A>=

B<

C"Pass"

D"Fail"

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of >= in the condition.

Swapping the strings "Pass" and "Fail".

The condition checks if score >= 50. If true, grade is "Pass", else "Fail".

5fill in blank

hard

Fill all three blanks to create a ternary expression that assigns the maximum of x and y to max.

Java

int x = 15;
int y = 25;
int max = ([1] [2] [3]) ? x : y;

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

Ax

By

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > in the condition.

Swapping x and y in the condition or result.

The ternary operator checks if x > y. If true, max is x, otherwise y.

Practice

1. What does the ternary operator condition ? valueIfTrue : valueIfFalse do in Java?

easy

A. It creates a loop that runs twice.

B. It chooses one of two values based on the condition's truth.

C. It declares a new variable.

D. It throws an error if the condition is false.

Solution

1. Step 1: Understand the ternary operator syntax

   The ternary operator uses a condition followed by a question mark, then two values separated by a colon.

2. Step 2: Determine its purpose

   It returns the first value if the condition is true, otherwise the second value.

3. Final Answer:

   It chooses one of two values based on the condition's truth. -> Option B

4. Quick Check:

   condition ? trueValue : falseValue = chooses value [OK]

Hint: Think: condition true? pick first : else pick second [OK]

Common Mistakes:

• Confusing ternary with loops
• Thinking it declares variables
• Assuming it throws errors automatically

2. Which of the following is the correct syntax for a ternary operator in Java?

easy

A. int result = (x > 0) ? (1 : -1);

B. int result = (x > 0) ? 1, -1;

C. int result = (x > 0) : 1 ? -1;

D. int result = (x > 0) ? 1 : -1;

Solution

1. Step 1: Review ternary operator syntax

   The correct syntax is: condition ? valueIfTrue : valueIfFalse;

2. Step 2: Check each option

   int result = (x > 0) ? 1 : -1; matches the correct syntax exactly. Others have wrong punctuation or order.

3. Final Answer:

   int result = (x > 0) ? 1 : -1; -> Option D

4. Quick Check:

   condition ? trueValue : falseValue syntax [OK]

Hint: Remember: question mark then colon separate values [OK]

Common Mistakes:

• Using comma instead of colon
• Swapping question mark and colon
• Adding extra parentheses incorrectly

3. What is the output of this Java code?

int a = 5;
int b = 10;
int max = (a > b) ? a : b;
System.out.println(max);

medium

A. 10

B. false

C. true

D. 5

Solution

1. Step 1: Evaluate the condition (a > b)

   Since a=5 and b=10, 5 > 10 is false.

2. Step 2: Apply ternary operator

   Because condition is false, max gets value b, which is 10.

3. Final Answer:

   10 -> Option A

4. Quick Check:

   (5 > 10) ? 5 : 10 = 10 [OK]

Hint: Check condition result true or false to pick value [OK]

Common Mistakes:

• Choosing the first value always
• Confusing variable values
• Expecting boolean output

4. Identify the error in this code snippet:

int x = 10;
int y = 20;
int min = x > y ? x, y;
System.out.println(min);

medium

A. Missing colon ':' in ternary operator

B. Incorrect variable declaration

C. Using comma instead of semicolon

D. No error, code runs fine

Solution

1. Step 1: Check ternary operator syntax

   The ternary operator requires a colon ':' between true and false values.

2. Step 2: Identify the error in code

   The code uses a comma ',' instead of a colon ':', causing a syntax error.

3. Final Answer:

   Missing colon ':' in ternary operator -> Option A

4. Quick Check:

   condition ? valueIfTrue : valueIfFalse needs ':' [OK]

Hint: Ternary needs '?' then ':'; commas cause errors [OK]

Common Mistakes:

• Using comma instead of colon
• Forgetting colon entirely
• Misplacing semicolons inside ternary

5. Given this code, what is the value of result?

int score = 75;
String result = (score >= 90) ? "A" : (score >= 80) ? "B" : (score >= 70) ? "C" : "F";
System.out.println(result);

hard

A. "A"

B. "B"

C. "C"

D. "F"

Solution

1. Step 1: Evaluate nested ternary conditions in order

   score=75. Check if score >= 90? No. Then check if score >= 80? No. Then check if score >= 70? Yes.

2. Step 2: Assign value based on first true condition

   Since score >= 70 is true, result is assigned "C".

3. Final Answer:

   "C" -> Option C

4. Quick Check:

   Nested ternary picks first true condition value [OK]

Hint: Read nested ternary top to bottom, pick first true [OK]

Common Mistakes:

• Stopping at first false condition
• Ignoring nested ternary order
• Confusing string quotes