The if-else statement in Java allows you to execute one block of code if a specified condition is true and a different block of code if the condition is false. This control structure is useful for making decisions in your program based on certain conditions.

Syntax of if-else Statement

if (condition) {
    // Block of code to be executed if the condition is true
} else {
    // Block of code to be executed if the condition is false
}

• condition: A boolean expression that evaluates to either true or false.
• True Block: The code inside the first set of braces {} executes if the condition is true.
• False Block: The code inside the second set of braces {} executes if the condition is false.

Example of if-else Statement

Here’s a simple example demonstrating the use of an if-else statement:

public class IfElseStatementExample {
    public static void main(String[] args) {
        int number = 5;

        // Using if-else statement to check if the number is positive or negative
        if (number > 0) {
            System.out.println("The number is positive.");
        } else {
            System.out.println("The number is not positive.");
        }
    }
}

Explanation

1. Declaration: The variable number is declared and initialized with the value 5.
2. Condition Check: The if statement checks whether number > 0. Since 5 is greater than 0, the condition evaluates to true.
3. Execution: Because the condition is true, the code inside the if block (System.out.println("The number is positive.");) is executed.
4. Output: The output will be:

   The number is positive.
   

Example with Different Conditions

Here’s another example that checks if a number is positive, negative, or zero using an if-else statement:

public class IfElseStatementMultipleConditions {
    public static void main(String[] args) {
        int number = 0;

        // Using if-else statement to check if the number is positive, negative, or zero
        if (number > 0) {
            System.out.println("The number is positive.");
        } else if (number < 0) {
            System.out.println("The number is negative.");
        } else {
            System.out.println("The number is zero.");
        }
    }
}

Explanation

In this example:

• The program checks three different conditions:
  • If number is greater than 0 (positive).
  • If number is less than 0 (negative).
  • If number is equal to 0 (zero).
• Since number is 0, the output will be:

  The number is zero.
  

Summary

The if-else statement is a fundamental control structure in Java that allows you to implement conditional logic in your programs. It enables you to choose between two paths of execution based on whether a certain condition is true or false. This makes your applications more dynamic and responsive to various input scenarios.