The Project | About Us | Contribute | Donations | License
HOME My courses Completed
◄ Previous
◄

Conditional Statements

Next ►
►

Conditional statements are fundamental in programming as they allow you to execute different blocks of code based on certain conditions. In Java, the primary conditional statements are if, if-else, if-else-if, and switch.

  1. if Statement

The if statement is used to execute a block of code only if a specified condition is true.

Syntax:

if (condition) {
    // code to be executed if condition is true
}

Example:

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

Explanation:

  • The condition number > 0 is checked.
  • If the condition is true, the message "The number is positive." is printed.

  1. if-else Statement

The if-else statement provides an alternative block of code to execute if the condition is false.

Syntax:

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

Example:

public class Main {
    public static void main(String[] args) {
        int number = -10;
        if (number > 0) {
            System.out.println("The number is positive.");
        } else {
            System.out.println("The number is not positive.");
        }
    }
}

Explanation:

  • The condition number > 0 is checked.
  • If the condition is true, the message "The number is positive." is printed.
  • If the condition is false, the message "The number is not positive." is printed.

  1. if-else-if Ladder

The if-else-if ladder is used to check multiple conditions.

Syntax:

if (condition1) {
    // code to be executed if condition1 is true
} else if (condition2) {
    // code to be executed if condition2 is true
} else {
    // code to be executed if all conditions are false
}

Example:

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

  • The condition number > 0 is checked first.
  • If the condition is true, the message "The number is positive." is printed.
  • If the condition is false, the next condition number < 0 is checked.
  • If the second condition is true, the message "The number is negative." is printed.
  • If both conditions are false, the message "The number is zero." is printed.

  1. switch Statement

The switch statement is used to execute one block of code among many based on the value of a variable.

Syntax:

switch (expression) {
    case value1:
        // code to be executed if expression == value1
        break;
    case value2:
        // code to be executed if expression == value2
        break;
    // you can have any number of case statements
    default:
        // code to be executed if none of the cases are true
}

Example:

public class Main {
    public static void main(String[] args) {
        int day = 3;
        switch (day) {
            case 1:
                System.out.println("Monday");
                break;
            case 2:
                System.out.println("Tuesday");
                break;
            case 3:
                System.out.println("Wednesday");
                break;
            case 4:
                System.out.println("Thursday");
                break;
            case 5:
                System.out.println("Friday");
                break;
            case 6:
                System.out.println("Saturday");
                break;
            case 7:
                System.out.println("Sunday");
                break;
            default:
                System.out.println("Invalid day");
                break;
        }
    }
}

Explanation:

  • The value of day is checked against each case.
  • If day is 3, the message "Wednesday" is printed.
  • The break statement is used to exit the switch block once a match is found.
  • If no match is found, the default case is executed.

Practical Exercises

Exercise 1:

Write a Java program that checks if a number is even or odd using an if-else statement.

Solution:

public class Main {
    public static void main(String[] args) {
        int number = 5;
        if (number % 2 == 0) {
            System.out.println("The number is even.");
        } else {
            System.out.println("The number is odd.");
        }
    }
}

Exercise 2:

Write a Java program that prints the name of the month based on the number (1 for January, 2 for February, etc.) using a switch statement.

Solution:

public class Main {
    public static void main(String[] args) {
        int month = 4;
        switch (month) {
            case 1:
                System.out.println("January");
                break;
            case 2:
                System.out.println("February");
                break;
            case 3:
                System.out.println("March");
                break;
            case 4:
                System.out.println("April");
                break;
            case 5:
                System.out.println("May");
                break;
            case 6:
                System.out.println("June");
                break;
            case 7:
                System.out.println("July");
                break;
            case 8:
                System.out.println("August");
                break;
            case 9:
                System.out.println("September");
                break;
            case 10:
                System.out.println("October");
                break;
            case 11:
                System.out.println("November");
                break;
            case 12:
                System.out.println("December");
                break;
            default:
                System.out.println("Invalid month");
                break;
        }
    }
}

Common Mistakes and Tips

  • Forgetting the break statement in a switch case: This can lead to fall-through, where multiple cases are executed.
  • Using == for string comparison: Use .equals() method for comparing strings.
  • Not covering all possible cases: Always include a default case in a switch statement to handle unexpected values.

Conclusion

In this section, you learned about the different types of conditional statements in Java, including if, if-else, if-else-if, and switch. These constructs allow you to control the flow of your program based on various conditions. Practice the exercises provided to reinforce your understanding and prepare for more complex control flow mechanisms in the next module.

◄ Previous
◄
Next ►
►

Java Programming Course

Module 1: Introduction to Java

Module 2: Control Flow

Module 3: Object-Oriented Programming

Module 4: Advanced Object-Oriented Programming

Module 5: Data Structures and Collections

Module 6: Exception Handling

Module 7: File I/O

Module 8: Multithreading and Concurrency

Module 9: Networking

Module 10: Advanced Topics

Module 11: Java Frameworks and Libraries

Module 12: Building Real-World Applications

The Project | About Us | Contribute | Donations | License
© Copyright 2024. All rights reserved