Why conditional statements are needed in Java - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Java code with conditional statements?

Look at the Java code below. What will it print when run?

Java

public class Main {
    public static void main(String[] args) {
        int temperature = 30;
        if (temperature > 25) {
            System.out.println("It's hot outside.");
        } else {
            System.out.println("It's cool outside.");
        }
    }
}

A It's cool outside.

B Compilation error

C It's hot outside.

D No output

💡 Hint

Check the value of temperature and the condition in the if statement.

The variable temperature is 30, which is greater than 25, so the if block runs and prints "It's hot outside." The else block is skipped.

🧠 Conceptual

intermediate

Why do we use conditional statements in programming?

Which of the following best explains why conditional statements are needed in programs?

A To allow the program to make decisions and choose different actions based on conditions.

B To repeat a set of instructions multiple times automatically.

C To store multiple values in a single variable.

D To define functions that can be reused.

💡 Hint

Think about how programs can behave differently depending on data or user input.

Conditional statements let programs decide what to do next based on conditions. This makes programs flexible and able to handle different situations.

❓ Predict Output

advanced

What is the output of this nested if-else Java code?

Analyze the Java code and select the exact output it produces.

Java

public class Main {
    public static void main(String[] args) {
        int score = 75;
        if (score >= 90) {
            System.out.println("Grade: A");
        } else if (score >= 80) {
            System.out.println("Grade: B");
        } else if (score >= 70) {
            System.out.println("Grade: C");
        } else {
            System.out.println("Grade: F");
        }
    }
}

A Grade: C

B Grade: B

C Grade: F

D Grade: A

💡 Hint

Check which condition the score 75 satisfies first.

The score 75 is not >= 90 or >= 80, but it is >= 70, so the program prints "Grade: C".

🔧 Debug

advanced

What error does this Java code produce?

This Java code tries to use an if statement but has a mistake. What error will it cause?

Java

public class Main {
    public static void main(String[] args) {
        int x = 10;
        if (x > 5) {
            System.out.println("x is greater than 5");
        }
    }
}

A TypeError: Cannot compare int and boolean

B RuntimeException: Null pointer exception

C No error, prints 'x is greater than 5'

D SyntaxError: Missing parentheses around condition

💡 Hint

Check the syntax of the if statement condition.

In Java, the condition in an if statement must be inside parentheses. Missing them causes a syntax error.

🚀 Application

expert

How many times will the message print?

Consider this Java code that uses a conditional inside a loop. How many times will it print "Number is even"?

Java

public class Main {
    public static void main(String[] args) {
        for (int i = 1; i <= 10; i++) {
            if (i % 2 == 0) {
                System.out.println("Number is even");
            }
        }
    }
}

A 10

B 5

C 0

D 1

💡 Hint

Count how many numbers from 1 to 10 are even.

The loop runs from 1 to 10. The condition checks if the number is even. Even numbers between 1 and 10 are 2,4,6,8,10 — 5 times.

Practice

1. Why do we need conditional statements like if in Java programs?

easy

A. To make decisions and run different code based on conditions

B. To repeat the same code multiple times

C. To store multiple values in a list

D. To define a new class or method

Solution

1. Step 1: Understand the purpose of conditional statements

   Conditional statements allow the program to choose different paths based on true or false conditions.

2. Step 2: Compare with other options

   Loops repeat code, lists store values, and classes define structure, but only conditionals make decisions.

3. Final Answer:

   To make decisions and run different code based on conditions -> Option A

4. Quick Check:

   Conditional statements = decision making [OK]

Hint: Conditionals = choosing between options [OK]

Common Mistakes:

• Confusing conditionals with loops
• Thinking conditionals store data
• Mixing conditionals with class definitions

2. Which of the following is the correct syntax to start a conditional statement in Java?

easy

A. switch condition { }

B. for (condition) { }

C. while condition { }

D. if (condition) { }

Solution

1. Step 1: Identify the syntax for an if statement

   The correct syntax uses the keyword if followed by parentheses around the condition and curly braces for the code block.

2. Step 2: Check other options

   for and while are loops, and switch has a different syntax with cases.

3. Final Answer:

   if (condition) { } -> Option D

4. Quick Check:

   if statement syntax = if (condition) { } [OK]

Hint: If starts with 'if' and parentheses [OK]

Common Mistakes:

• Using loop keywords instead of if
• Missing parentheses around condition
• Using switch syntax for if

3. What will be the output of this Java code?

int x = 10;
if (x > 5) {
  System.out.println("Greater");
} else {
  System.out.println("Smaller");
}

medium

A. 10

B. Greater

C. Smaller

D. No output

Solution

1. Step 1: Evaluate the condition x > 5

   Since x is 10, which is greater than 5, the condition is true.

2. Step 2: Determine which block runs

   The if block runs and prints "Greater"; the else block is skipped.

3. Final Answer:

   Greater -> Option B

4. Quick Check:

   10 > 5 is true, so prints "Greater" [OK]

Hint: Check if condition is true or false [OK]

Common Mistakes:

• Choosing else output when condition is true
• Confusing printed value with variable value
• Ignoring the else block

4. Find the error in this Java code snippet:

int num = 7;
if num > 5 {
  System.out.println("Yes");
} else {
  System.out.println("No");
}

medium

A. Missing parentheses around the condition in if statement

B. Missing semicolon after if statement

C. Incorrect use of else keyword

D. Variable num is not declared

Solution

1. Step 1: Check the if statement syntax

   The condition in an if statement must be inside parentheses, but here it is missing.

2. Step 2: Verify other parts

   Semicolons are not needed after if conditions, else is correctly used, and variable num is declared.

3. Final Answer:

   Missing parentheses around the condition in if statement -> Option A

4. Quick Check:

   if condition needs parentheses [OK]

Hint: If condition always inside ( ) [OK]

Common Mistakes:

• Forgetting parentheses in if
• Adding semicolon after if condition
• Thinking else needs parentheses

5. You want to write a Java program that prints "Adult" if age is 18 or more, "Teen" if age is between 13 and 17, and "Child" otherwise. Which conditional structure correctly implements this?

hard

A. if (age > 18) { System.out.println("Adult"); } else if (age > 13) { System.out.println("Teen"); } else { System.out.println("Child"); }

B. if (age >= 18) { System.out.println("Adult"); } else if (age > 13 && age < 18) { System.out.println("Teen"); } else { System.out.println("Child"); }

C. if (age >= 18) { System.out.println("Adult"); } else if (age >= 13) { System.out.println("Teen"); } else { System.out.println("Child"); }

D. if (age > 18) { System.out.println("Adult"); } else if (age >= 13 && age <= 17) { System.out.println("Teen"); } else { System.out.println("Child"); }

Solution

1. Step 1: Check the age ranges for each category

   Adult is 18 or more, Teen is 13 to 17 inclusive, Child is below 13.

2. Step 2: Analyze each option's conditions

   if (age >= 18) { System.out.println("Adult"); } else if (age >= 13) { System.out.println("Teen"); } else { System.out.println("Child"); } uses >= 18 for Adult, >= 13 for Teen (which covers 13 to 17), else Child. This matches the requirement exactly.

3. Final Answer:

   if (age >= 18) { System.out.println("Adult"); } else if (age >= 13) { System.out.println("Teen"); } else { System.out.println("Child"); } -> Option C

4. Quick Check:

   Correct age ranges with if-else if-else [OK]

Hint: Check boundary conditions carefully [OK]

Common Mistakes:

• Using > instead of >= causing wrong category
• Overlapping or missing age ranges
• Incorrect else if conditions order