If Else

A school program needs reliable data and clear rules. An if-else statement chooses exactly one of two branches. A student either meets this report’s pass threshold or needs further practice.

In Java, the if-else statement is used to make decisions in your program. It checks a condition and runs different code depending on whether the condition is true or false.

For example: if it rains, you stay home; else, you go outside. That's how if-else works.

if (condition) {
    // Runs if condition is true
} else {
    // Runs if condition is false
}

• condition: This is a boolean expression that evaluates to either true or false.
• If the condition evaluates to true, the code block inside the if block runs.
• If the condition is false, the code block inside the else block runs instead.

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

The number is positive.

public class Main {
    public static void main(String[] args) {
        int number = 7;
        if (number % 2 == 0) {
            System.out.println("Even number");
        } else {
            System.out.println("Odd number");
        }
    }
}

Odd number

Sometimes you want to check another condition only if the first one passes. That’s when nesting helps.

public class Main {
    public static void main(String[] args) {
        int age = 20;
        int score = 85;

        if (age >= 18) {
            if (score > 80) {
                System.out.println("Eligible for scholarship.");
            } else {
                System.out.println("Eligible, but no scholarship.");
            }
        } else {
            System.out.println("Not eligible.");
        }
    }
}

Eligible for scholarship.

• if checks a condition and runs code when it’s true.
• else provides an alternate path when the if fails.
• if-else-if allows multiple conditions to be checked in order.
• Nested if helps for dependent checks.

public class Main {
    public static void main(String[] args) {
        String username = "admin";
        String password = "1234859";

        if (username.equals("admin")) {
            if (password.equals("1234")) {
                System.out.println("Login successful!");
            } else {
                System.out.println("Incorrect password.");
            }
        } else {
            System.out.println("Username not found.");
        }
    }
}

Login successful!

Two separate if statements are not the same as one if-else decision: both independent conditions could be true.

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: Two separate if statements are not the same as one if-else decision: both independent conditions could be true..

Java 17 · Main.java · complete practice program

public class Main  {
  public static void main(String[] args)  {
    int marks = 40;
    if (marks >= 50)  {
      System.out.println("Pass");
    }
    else  {
      System.out.println("Practise");
    }
  }
}

Now change one thing: Change marks to 72. Predict the new behavior before checking the worked variation.

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

public class Main  {
  public static void main(String[] args)  {
    int marks = 40;
    if (marks >= 50)  {
      System.out.println("Pass");
    }
    else  {
      System.out.println("Practise");
    }
  }
}

Expected output

Practise

An if-else statement chooses exactly one of two branches. A student either meets this report’s pass threshold or needs further practice.

Two separate if statements are not the same as one if-else decision: both independent conditions could be true.

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.

Worked variation: Change marks to 72. The Pass branch runs and the Practise branch does not.

An if-else statement chooses exactly one of two branches. A student either meets this report’s pass threshold or needs further practice. Two separate if statements are not the same as one if-else decision: both independent conditions could be true.

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.