Java If Statement
Syntax and Examples

The if statement in Java is like a gate. It opens only if a certain condition is true. Otherwise, it quietly ignores the code block inside it. This simple control structure forms the basis for decision-making in Java programs.

Syntax of If Statement in Java

if (condition) {
    // code to execute if condition is true
}

The condition must evaluate to a sboolean value, either true or false. If it's true, the code inside the block executes. If not, the program simply skips that block and moves on.

Example 1: Basic Java If Statement

public class IfExample1 {
    public static void main(String[] args) {
        int number = 10;
        if (number > 0) {
            System.out.println("The number is positive.");
        }
        System.out.println("Program ended.");
    }
}

The number is positive.
Program ended.

Explanation:

Since number > 0 evaluates to true, the message inside the if block is printed. The last line runs regardless of the condition.

Step-by-Step Execution Flow:

1. Variable number is assigned 10.
2. The condition number > 0 becomes true.
3. The message is printed.
4. The program continues with the next statement after the if block.

Example 2: Condition That Fails

public class IfExample2 {
    public static void main(String[] args) {
        int age = 15;
        if (age >= 18) {
            System.out.println("You can vote.");
        }
        System.out.println("Check completed.");
    }
}

Check completed.

Explanation:

Here, the condition age >= 18 is false. So, the code inside the if block is ignored. Only the final line runs.

Best Practices When Using If Statements

• Always ensure your condition is boolean: Non-boolean conditions won't compile in Java.
• Use braces { } even for single-line blocks: It improves readability and helps avoid logical bugs.
• Keep your conditions clear and readable: Use meaningful variable names and avoid overly complex expressions.

Common Mistakes to Avoid

• Using = instead of ==: Assignment vs. comparison. if (a = 10) is invalid. Use == for comparison.
• Forgetting curly braces: Without them, only the next line is considered part of the if block.
• Writing semicolon after if condition: if (x > 0); { ... } causes logic errors. That semicolon ends the if prematurely.

Example 3: No Curly Braces – What Happens?

public class IfExample3 {
    public static void main(String[] args) {
        int marks = 85;
        if (marks > 50)
            System.out.println("You passed!");
            System.out.println("This message is outside the if.");
    }
}

You passed!
This message is outside the if.

Explanation:

Only the first print statement is inside the if. The second line executes every time. To avoid such surprises, always use curly braces.

Summary

The Java if statement allows your programs to make decisions. Always test your conditions, keep your code readable, and avoid syntax pitfalls. As you progress, if will serve as a foundation for more advanced constructs like else, else if, and switch statements.