Nested if

1. What is a Nested if?

A nested if is an if statement placed inside another if (or else) block. It's used when a decision only makes sense after another condition has already been satisfied.

2. Why is it used?

Some decisions genuinely depend on multiple layers of conditions — like first checking if a user is logged in, and only then checking if they have admin access. Nested if handles this layered logic.

3. Real-Life Example

Think of entry rules at a club: "If you are 18 or older, then check if you have a valid ID. If both are true, you're allowed in." The ID check only matters once the age condition is already satisfied.

4. Syntax

java
if (condition1) {
    if (condition2) {
        // runs only if both condition1 and condition2 are true
    }
}

5. Example Program

java
public class NestedIfDemo {
    public static void main(String[] args) {
        int age = 20;
        boolean hasID = true;

        if (age >= 18) {
            if (hasID) {
                System.out.println("Entry allowed");
            } else {
                System.out.println("ID required");
            }
        } else {
            System.out.println("Not old enough");
        }
    }
}

Output:

Entry allowed

6. Key Points to Remember

• Nested if is useful when a condition is only relevant after another condition passes.
• Too many nested levels make code hard to read — consider combining conditions with && instead when possible.
• Proper indentation is important to keep nested blocks readable.