**Course Title:** Comprehensive Java Programming: From Basics to Advanced Concepts **Section Title:** Control Flow Statements in Java **Topic:** Conditional statements: if-else, switch-case. ### Introduction to Conditional Statements In programming, conditional statements are used to make decisions based on conditions or rules. These statements execute different blocks of code depending on the outcome of the conditions. In this topic, we'll explore two essential types of conditional statements in Java: if-else and switch-case. **Why Use Conditional Statements?** Conditional statements improve the flexibility and efficiency of your code. By allowing your program to adapt to different situations, you can: 1. Handle various input scenarios 2. Make decisions based on user input, data, or other conditions 3. Improve code readability by avoiding repetitive code ### If-Else Statements The if-else statement is the most commonly used conditional statement in Java. It consists of three parts: 1. `if` clause: specifies the condition 2. `else` clause (optional): executes when the condition is false 3. `else if` clause (optional): executes when the initial condition is false and the subsequent condition is true **Syntax:** ```java if (condition) { // execute this code if condition is true } else { // execute this code if condition is false } ``` **Example 1: Simple If-Else Statement** ```java int age = 20; if (age >= 18) { System.out.println("You are eligible to vote."); } else { System.out.println("You are not eligible to vote."); } ``` **Example 2: If-Else If-Else Statement** ```java int score = 75; if (score >= 90) { System.out.println("Excellent score!"); } else if (score >= 70 && score < 90) { System.out.println("Good score!"); } else { System.out.println("You need to improve."); } ``` ### Switch-Case Statements The switch-case statement is an alternative to if-else statements when dealing with a single variable that can take multiple values. It's more efficient than if-else when: 1. You have multiple cases to check 2. The variable is an integer, character, or enum **Syntax:** ```java switch (expression) { case value1: // execute this code if expression equals value1 break; case value2: // execute this code if expression equals value2 break; default: // execute this code if expression doesn't match any value break; } ``` **Example:** ```java int day = 5; switch (day) { case 1: System.out.println("Monday"); break; case 2: System.out.println("Tuesday"); break; case 3: System.out.println("Wednesday"); break; default: System.out.println("Invalid day"); break; } ``` ### When to Use If-Else vs Switch-Case 1. Use if-else for: * Complex conditions with multiple operators * Variables with non-integer data types (e.g., strings, booleans) * Situations where you need to execute multiple statements 2. Use switch-case for: * Single variables with multiple values * Performance-critical sections of code * Simplifying large if-else chains ### Practice Time Try these exercises to reinforce your understanding of if-else and switch-case statements: 1. Write an if-else statement to check if a person is eligible for a discount based on their age. 2. Create a switch-case statement to determine the cost of shipping based on the destination state. 3. Use a combination of if-else and switch-case to validate user input and display an error message. ### Conclusion Conditional statements are a fundamental aspect of programming. By mastering if-else and switch-case statements, you'll be able to write more efficient and effective code. Remember to choose the right statement based on the specific problem and use cases. **What's Next?** In the next topic, we'll explore **Loops in Java: for, while, do-while**. Loops will help you execute blocks of code repeatedly, making your programs more efficient and scalable. **External Resources:** * Oracle Java Documentation: [If Statements](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/if.html) * Oracle Java Documentation: [Decision Making with Switch](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/switch.html) **Leave a Comment/Ask for Help** Please feel free to leave a comment or ask for help if you have any questions or need further clarification on conditional statements.