Control Flow Statements (if, else, switch, loops)

Control flow statements are essential for controlling the flow of execution in a Java program. They allow you to make decisions, repeat blocks of code, and execute code based on conditions. Let's explore the main control flow statements in Java: `if`, `else`, `switch`, and loops.

1. if Statement

The `if` statement allows you to execute a block of code if a specified condition is true.

int num = 10;
if (num > 0) {
    System.out.println("The number is positive.");
}

2. if-else Statement

The `if-else` statement allows you to execute one block of code if a condition is true and another block of code if the condition is false.

int num = -5;
if (num > 0) {
    System.out.println("The number is positive.");
} else {
    System.out.println("The number is non-positive.");
}

3. Nested if-else Statement

You can nest `if-else` statements to handle multiple conditions.

int num = 0;
if (num > 0) {
    System.out.println("The number is positive.");
} else if (num < 0) {
    System.out.println("The number is negative.");
} else {
    System.out.println("The number is zero.");
}

4. switch Statement

The `switch` statement allows you to select one of many code blocks to be executed.

int day = 3;
String dayName;
switch (day) {
    case 1:
        dayName = "Monday";
        break;
    case 2:
        dayName = "Tuesday";
        break;
    case 3:
        dayName = "Wednesday";
        break;
    // Add cases for other days...
    default:
        dayName = "Unknown";
}
System.out.println("Today is " + dayName);

5. Loops

Loops are used to execute a block of code repeatedly as long as a specified condition is true.

a. while Loop

The `while` loop executes a block of code as long as the specified condition is true.

int i = 1;
while (i <= 5) {
    System.out.println("Count: " + i);
    i++;
}

b. do-while Loop

The `do-while` loop is similar to the `while` loop, but it guarantees that the block of code is executed at least once, even if the condition is false.

int i = 1;
do {
    System.out.println("Count: " + i);
    i++;
} while (i <= 5);

c. for Loop

The `for` loop is used to iterate over a range of values.

for (int i = 1; i <= 5; i++) {
    System.out.println("Count: " + i);
}

d. Enhanced for Loop (for-each Loop)

The enhanced `for` loop is used to iterate over elements in an array or a collection.

int[] numbers = {1, 2, 3, 4, 5};
for (int num : numbers) {
    System.out.println("Number: " + num);
}

Conclusion

Control flow statements such as `if`, `else`, `switch`, and loops (`while`, `do-while`, `for`) are essential for writing flexible and efficient Java programs. They allow you to make decisions, handle different cases, and repeat code as needed. Understanding how to use these control flow statements effectively is crucial for becoming proficient in Java programming.