If-Else Statement in Java

In this tutorial, we will learn about if-else statements in Java. We will cover the basics of conditional execution using if-else statements.

What is an If-Else statement

An if-else statement is a conditional statement that executes one block of code if a specified condition is true, and another block of code if the condition is false.

Syntax

The syntax for the if-else statement in Java is:

if (condition) {
    // Code block to execute if condition is true
} else {
    // Code block to execute if condition is false
}

The if-else statement evaluates the specified condition. If the condition is true, the code block inside the if statement is executed; otherwise, the code block inside the else statement is executed.

Flowchart of If Else Statement

Example 1: Checking if a Number is Even or Odd

  1. Declare an integer variable num.
  2. Assign a value to num.
  3. Use an if-else statement to check if num is even or odd.
  4. Print a message indicating whether num is even or odd.

Java Program

public class Main {
    public static void main(String[] args) {
        int num = 10;
        if (num % 2 == 0) {
            System.out.printf("%d is even.%n", num);
        } else {
            System.out.printf("%d is odd.%n", num);
        }
    }
}

Output

10 is even.

Example 2: Checking if a String Starts with a Specific Value

  1. Declare a string variable str.
  2. Assign a value to str.
  3. Use an if-else statement to check if str starts with a specific value.
  4. Print a message indicating the result of the check.

Java Program

public class Main {
    public static void main(String[] args) {
        String str = "Hello, world!";
        if (str.startsWith("Hello")) {
            System.out.println("String starts with 'Hello'.");
        } else {
            System.out.println("String does not start with 'Hello'.");
        }
    }
}

Output

String starts with 'Hello'.

Example 3: Checking if a Number is Positive or Negative

  1. Declare an integer variable num.
  2. Assign a value to num.
  3. Use an if-else statement to check if num is positive or negative.
  4. Print a message indicating whether num is positive or negative.

Java Program

public class Main {
    public static void main(String[] args) {
        int num = -5;
        if (num > 0) {
            System.out.printf("%d is positive.%n", num);
        } else {
            System.out.printf("%d is negative or zero.%n", num);
        }
    }
}

Output

-5 is negative or zero.