Conditional Statements

A school program needs reliable data and clear rules. A condition chooses which instructions run. A school report can distinguish passing from needing practice, while instructions after the decision still run.

Conditional statements allow your program to choose different paths of execution depending on whether a condition is true or false. Think of them as the 'brain' of your logic – making choices on your behalf.

Java provides several ways to handle conditions:

• if statement
• if-else statement
• else-if ladder
• switch statement

The if statement checks a condition and executes the block of code inside it only if the condition is true.

public class IfExample {
    public static void main(String[] args) {
        int number = 10;
        if (number > 0) {
            System.out.println("The number is positive.");
        }
    }
}

The number is positive.

Explanation

The program checks if number > 0. Since 10 is greater than 0, it prints the message.

If the number were negative, nothing would be printed.

public class IfExample {
    public static void main(String[] args) {
        int number = -5;
        if (number > 0) {
            System.out.println("The number is positive.");
        }
    }
}

Explanation

The program checks if number > 0. Since -5 is not greater than 0, if block does not execute and nothing has been printed.

Use this when you have two scenarios — one when the condition is true and another when it's false.

public class IfElseExample {
    public static void main(String[] args) {
        int number = -5;
        if (number >= 0) {
            System.out.println("Non-negative number");
        } else {
            System.out.println("Negative number");
        }
    }
}

Negative number

Since the given condition is false, else block executes.

This pattern is useful when your program must respond differently depending on a single true/false condition.

When you have multiple conditions to evaluate in a sequence, else-if ladders help maintain readability and logic flow.

public class ElseIfExample {
    public static void main(String[] args) {
        int score = 85;
        if (score >= 90) {
            System.out.println("Grade A");
        } else if (score >= 75) {
            System.out.println("Grade B");
        } else if (score >= 60) {
            System.out.println("Grade C");
        } else {
            System.out.println("Fail");
        }
    }
}

Grade B

Verification Tip

Start with the highest condition and work your way down to the least. This avoids overlapping ranges or incorrect classifications.

Use a switch when you have a single variable that can take multiple constant values (like enums, numbers, or strings in Java 7+).

public class SwitchExample {
    public static void main(String[] args) {
        int day = 3;
        switch (day) {
            case 1:
                System.out.println("Monday");
                break;
            case 2:
                System.out.println("Tuesday");
                break;
            case 3:
                System.out.println("Wednesday");
                break;
            default:
                System.out.println("Another day");
        }
    }
}

Wednesday

Important Checks

• Always include a break statement to prevent fall-through unless you want cumulative behavior.
• Include a default case to handle unexpected inputs.

Java · example discussed here

public class SwitchExample {
    public static void main(String[] args) {
        int day = 3;
        switch (day) {
            case 1:
                System.out.println("Monday");
                break;
            case 2:
                System.out.println("Tuesday");
                break;
            case 3:
                System.out.println("Wednesday");
                break;
            default:
                System.out.println("Another day");
        }
    }
}

• Forgetting break in switch, which may lead to incorrect results.
• Using assignment = instead of comparison == in conditions.
• Improper nesting of if-else, leading to confusion and logic errors.

An if condition must be boolean. A chain stops at its first matching branch, so the order of thresholds matters.

Before running this Java program, write down each line you expect to see. Identify the value, branch, object or exception responsible for each line. Then explain whether the following assumption is valid: An if condition must be boolean.

Java 17 · Main.java · complete practice program

public class Main  {
  public static void main(String[] args)  {
    int marks = 72;
    if (marks >= 50)  {
      System.out.println("Pass");
    }
    else  {
      System.out.println("Practise");
    }
  }
}

Java 17 · Main.java · source repeated for this answer

public class Main  {
  public static void main(String[] args)  {
    int marks = 72;
    if (marks >= 50)  {
      System.out.println("Pass");
    }
    else  {
      System.out.println("Practise");
    }
  }
}

Expected output

Pass

A condition chooses which instructions run. A school report can distinguish passing from needing practice, while instructions after the decision still run.

An if condition must be boolean. A chain stops at its first matching branch, so the order of thresholds matters.

Run with javac Main.java, then java Main. The declaration of Main names the class; main starts the example, and println writes a complete output line.

A condition chooses which instructions run. A school report can distinguish passing from needing practice, while instructions after the decision still run. An if condition must be boolean. A chain stops at its first matching branch, so the order of thresholds matters.

Related explanations: Java Variables, Java If Statement - Syntax and Examples, Java Class - Blueprint of Objects, Exceptions in Java Introduction.

Supporting documentation: Official Java learning guide and Java 17 language specification.