If-Else Statement in Java

In the previous example, we used if to handle one situation.

For example:

If the user is under 18, show an underage message.

But there was a problem.

What should happen when the user is 18 or older?

With only an if statement, we weren't doing anything.

Now imagine a security gate. The rule is:

If the person is under 18, deny access. Otherwise, grant access.

Now we have two possible outcomes.

This is where the if-else statement becomes useful.

What is if-else?

The basic syntax is:

if (condition) {
    // executes when condition is true
} else {
    // executes when condition is false
}

The difference from a simple if is that else gives Java an alternative path.

Think about it like this:

             Condition
                 ↓
          ┌──────┴──────┐
        true           false
          ↓               ↓
      if block        else block

If the condition is true, the if block executes.

If the condition is false, the else block executes.

And notice something important:

else does not have a condition.

Why?

Because else represents what should happen when the if condition is not satisfied.

Real-World Example: Access Control

Let's say we are building a simple access-control system.

Our requirement is:

• Under 18 → Access Denied

• 18 or older → Access Granted

We can write:

if (age < 18) {
    System.out.println("Access Denied");
} else {
    System.out.println("Access Granted");
}

Suppose the user enters:

12

Java checks:

12 < 18

The condition is true.

Therefore, the if block executes:

Access Denied

Now suppose the user enters:

45

Java checks:

45 < 18

The condition is false.

So Java skips the if block and executes the else block.

Output:

Access Granted

Why Do We Need else?

Let's compare this with our previous if example.

With only if:

if (age < 18) {
    System.out.println("Access Denied");
}

If the age is 12, we get:

Access Denied

But if the age is 45, nothing happens.

Now add else:

if (age < 18) {
    System.out.println("Access Denied");
} else {
    System.out.println("Access Granted");
}

Now every situation has an outcome.

Age < 18
   ↓
Access Denied

Age >= 18
   ↓
Access Granted

This makes if-else particularly useful when you have two possible paths.

Understanding the Execution Flow

Let's say:

int age = 16;

if (age < 18) {
    System.out.println("Access Denied");
} else {
    System.out.println("Access Granted");
}

Java starts with the condition:

age < 18

Substitute the value:

16 < 18

This is true.

So Java executes the if block.

It does not execute the else block.

Now change the age:

int age = 25;

The condition becomes:

25 < 18

This is false.

So Java executes the else block.

It does not execute the if block.

Therefore, in an if-else statement, Java chooses between the two blocks based on the condition.

Another Real-Life Way to Think About It

Imagine a door with an age restriction.

The system asks:

Is the person under 18?

If yes:

Access Denied

Otherwise:

Access Granted

There is no third option in our current requirement.

That's exactly what if-else represents.

IF this condition is true
    → do this

ELSE
    → do the other thing

Key Takeaway

Use if-else when your program needs to handle two possible outcomes.

if (condition) {
    // first possibility
} else {
    // second possibility
}

Remember:

if handles the condition being true, while else handles the condition being false.