Ternary operator in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested ternary operator

What is the output of the following Java code?

Java

public class Main {
    public static void main(String[] args) {
        int x = 5;
        String result = x > 0 ? (x < 10 ? "Small" : "Medium") : "Negative";
        System.out.println(result);
    }
}

A Compilation error

B Medium

C Negative

D Small

💡 Hint

Check the conditions in the nested ternary carefully.

The variable x is 5, which is greater than 0, so the first condition is true. Then it checks if x < 10, which is also true, so it returns "Small".

❓ Predict Output

intermediate

Ternary operator with boolean expressions

What will be printed by this Java program?

Java

public class Main {
    public static void main(String[] args) {
        boolean a = true;
        boolean b = false;
        String output = a ? (b ? "Both true" : "Only a true") : "a is false";
        System.out.println(output);
    }
}

A Only a true

B Both true

C a is false

D Compilation error

💡 Hint

Evaluate the conditions step by step.

Variable a is true, so the first condition is true. Then it checks b, which is false, so it returns "Only a true".

🔧 Debug

advanced

Identify the error in ternary usage

What error does this Java code produce?

Java

public class Main {
    public static void main(String[] args) {
        int x = 10;
        String result = x > 5 ? "Greater" : 5;
        System.out.println(result);
    }
}

A No error, prints "Greater"

B Type mismatch: cannot convert from int to String

C No error, prints "5"

D Syntax error: missing colon

💡 Hint

Check the types of both expressions in the ternary operator.

The ternary operator requires both expressions to be of compatible types. Here, one is String and the other is int, causing a type mismatch error.

🧠 Conceptual

advanced

Ternary operator evaluation order

Consider this Java code snippet:

int a = 3;
int b = 4;
int max = a > b ? a : b;

Which statement is true about how the ternary operator works here?

A Both a and b are evaluated before the ternary operator returns a value

B The ternary operator always evaluates both expressions regardless of the condition

C Only the expression corresponding to the true condition is evaluated

D The ternary operator evaluates neither expression and returns the condition's boolean value

💡 Hint

Think about short-circuit behavior in conditional expressions.

The ternary operator evaluates only the expression that matches the condition's result, not both.

❓ Predict Output

expert

Complex ternary operator with method calls

What is the output of this Java program?

Java

public class Main {
    static String check(int n) {
        return n % 2 == 0 ? "Even" : "Odd";
    }
    public static void main(String[] args) {
        int x = 7;
        String result = x > 5 ? check(x) : "Too small";
        System.out.println(result);
    }
}

A Odd

B Too small

C Compilation error

D Even

💡 Hint

Evaluate the condition and then the method call.

x is 7, which is greater than 5, so check(7) is called. 7 % 2 is 1, so it returns "Odd".

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