Ternary operator in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the ternary operator in Java?

The ternary operator is a shortcut for an if-else statement. It uses the syntax: condition ? valueIfTrue : valueIfFalse;

beginner

How does the ternary operator improve code?

It makes code shorter and easier to read when choosing between two values based on a condition.

beginner

Example: What does this code print?

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

It prints 10 because the condition (a > b) is false, so it chooses the value after the colon, which is b (10).

intermediate

Can the ternary operator be nested in Java?

Yes, you can nest ternary operators inside each other, but it can make code harder to read.

intermediate

What types of values can the ternary operator return?

It can return any type as long as both possible values are of compatible types (e.g., both int, or both String).

What is the correct syntax of the ternary operator in Java?

A condition : valueIfTrue ? valueIfFalse

B if (condition) then valueIfTrue else valueIfFalse

C condition ? valueIfTrue : valueIfFalse

D condition ? valueIfFalse : valueIfTrue

The ternary operator syntax is condition ? valueIfTrue : valueIfFalse.

What will this print?

int x = 3; System.out.println(x > 5 ? "Yes" : "No");

A Yes

B 3

C Error

D No

Since 3 > 5 is false, it prints the value after the colon: No.

Can the ternary operator replace all if-else statements?

A No, only simple if-else that return values

B Only for boolean variables

C Only for loops

D Yes, always

Ternary operator is best for simple if-else that choose between two values.

What happens if you nest ternary operators too much?

A Code becomes easier to read

B Code becomes harder to read and maintain

C Code runs faster

D It causes a syntax error

Nesting ternary operators can make code confusing and hard to maintain.

Which of these is a valid use of the ternary operator?

A int max = (a > b) ? a : b;

B int max = if (a > b) a else b;

C int max = a > b ? a, b;

D int max = a > b : a ? b;

Option A uses correct ternary syntax to assign max.

Explain how the ternary operator works in Java and give a simple example.

Think of it as a short if-else that picks one of two values.

What are the advantages and disadvantages of using the ternary operator?

Consider when it helps and when it might confuse.

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