Flow Control Statements in Java

In Java, flow control statements are fundamental to a program's logic. They enable you to guide the execution of code based on specific conditions, repeat actions, and make decisions.

Conditional Statements

if else

The `if` statement allows you to execute a block of code only when a certain condition is met, while the `else` statement provides an alternative for when that condition is not satisfied.

if (temperature > 30) {
    turnOnAirConditioning();
} else {
    turnOffAirConditioning();
}

In this example, the air conditioning is turned on if the temperature exceeds 30 degrees; otherwise, it’s turned off.

else if

When you need to evaluate multiple conditions within an if-else structure, the `else if` clause allows you to create a sequence of decisions.

if (day == "Monday") {
    print("The week is starting.");
} else if (day == "Friday") {
    print("The week is almost over.");
} else {
    print("It's a regular day.");
}

In this case, the program prints a different message depending on the day of the week.

switch

When you have a variable that can take one of several possible values, `switch` offers an efficient way to handle them.

switch (trafficSignal) {
    case "Red":
        stopCar();
        break;
    case "Yellow":
        prepareToStop();
        break;
    case "Green":
        goCar();
        break;
    default:
        signalError();
}

Depending on the traffic signal, the car will either stop, prepare to stop, or proceed.

Loops

Java provides three primary loop constructs: for, while, and do-while.

for

The `for` loop is ideal for running an operation a specific number of times.

for (int i = 0; i < 10; i++) {
    print("Count: " + i);
}

In this example, the loop prints the numbers from 0 to 9.

while

The `while` loop continues to execute a block of code as long as a given condition remains true.

while (notFinished()) {
    continueProcessing();
}

The loop keeps processing until the task is complete.

do-while

Similar to `while`, the `do-while` loop ensures that the code block is executed at least once, regardless of the condition.

do {
    requestInput();
} while (inputIsInvalid());

In this example, the user is prompted for input at least once, and the loop continues until the input is valid.

Jump Statements

break

The `break` statement is used to exit immediately from a loop or a `switch` statement.

for (int i = 0; i < 10; i++) {
    if (i == 5) {
        break; // Exits the loop when i is 5
    }
    print("Count: " + i);
}

continue

The `continue` statement skips the current iteration and moves on to the next one.

for (int i = 0; i < 10; i++) {
    if (i % 2 == 0) {
        continue; // Skips even numbers
    }
    print("Odd number: " + i);
}

return

The `return` statement ends the execution of a method and, if applicable, returns a value to the caller.

public int sum(int a, int b) {
    return a + b; // Returns the sum of a and b
}

These flow control statements are essential for constructing complex and adaptable logic in Java.

They empower you to create programs that dynamically respond to conditions and data encountered during execution.