3.3. Conditional Statements

These are used to execute code only when certain conditions are true.

Conditional statements allow your program to make decisions based on certain conditions. If a condition evaluates to true, the associated block of code will be executed. If the condition is false, the code within that block is skipped, allowing for more flexible and dynamic behavior in your programming.

Think of a traffic light. When the light is green, cars can go; when it is red, cars must stop. Similarly, conditional statements control whether certain actions in your program are executed based on specified conditions.

✅ A. if Statement Executes a block of code only if the condition is true.

int age = 18;
if (age >= 18) {
    System.out.println("You are eligible to vote.");
}

The if statement checks a specific condition (like whether a user is 18 years old or older). If the condition is true, it will execute the code inside the brackets. In this case, if age is 18 or more, it will print a message about voting eligibility. If age is less than 18, nothing happens.

Imagine a bouncer at a nightclub checking IDs. If the person is of legal age, they get in (the code executes); if not, they are turned away (no action is taken). The bouncer only allows people in when the condition (being of legal age) is true.

✅ B. if-else Statement Provides an alternative block if the condition is false.

int age = 16;
if (age >= 18) {
    System.out.println("You are eligible to vote.");
} else {
    System.out.println("You are not eligible to vote.");
}

The if-else statement allows for an alternative action if the condition is false. In this example, if the age is 16, the first condition (age >= 18) is false, so the program executes the 'else' block and prints that the user is not eligible to vote. This way, the program can handle two possible scenarios.

Think of a game where a player must reach a certain score to win. If they score enough points, they win; otherwise, they lose. The if-else structure handles both outcomes by directing the program flow based on the player's score.

✅ C. if-else-if Ladder Checks multiple conditions in sequence.

int marks = 75;
if (marks >= 90) {
    System.out.println("Grade A");
} else if (marks >= 75) {
    System.out.println("Grade B");
} else if (marks >= 50) {
    System.out.println("Grade C");
} else {
    System.out.println("Fail");
}

💡 Only the first true condition will execute; the rest are skipped.

The if-else-if ladder allows you to check multiple conditions. In this setup, if marks are 90 or above, it prints 'Grade A'; if marks are between 75 and 89, it prints 'Grade B', and so forth. Only the first true condition executes, making the program efficient by skipping unnecessary checks.

Imagine grading students based on their scores. If a student scores above 90, they get an A; between 75 and 89, they get a B, and so on. This ladder structure helps educators assign grades based on multiple criteria.

✅ D. Nested if Statement Placing an if inside another if.

int age = 20;
String citizen = "Indian";
if (age >= 18) {
    if (citizen.equals("Indian")) {
        System.out.println("Eligible to vote in India");
    }
}

A nested if statement means that you have an if statement within another if statement. In this example, the outer if checks if the age is 18 or above, and only then does it check if the citizen is 'Indian'. This structure is useful for situations where a condition depends on the truth of another condition.

Think of two checkpoints: first, verifying a person's age (like verifying they’re old enough to vote), then checking their nationality. Only when a person meets both criteria can they proceed to vote, which is similar to how nested condition checks function.

✅ E. switch Statement A cleaner way to handle multiple exact matches instead of many if-else.

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;
    default:
        System.out.println("Invalid day");
}

The switch statement is a simpler way to write multiple condition checks for certain specific values. Here, the program checks the value of 'day'. It matches the case (e.g., 3 for Wednesday) and prints the corresponding message. The 'break' statement stops further checks once a match is found, similar to exiting a room after finding what you needed.

Consider a meal ordering system at a restaurant. If you say '1,' it serves you pasta; if '2,' a salad; if '3,' a burger. A switch simplifies the decision-making process compared to having numerous if-else statements for each meal option.

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