Conditional Statements

Conditional statements choose which code to execute based on a boolean condition. They help a program respond to different inputs and situations.

if and else#

int score = 76;

if (score >= 90) {
    System.out.println("Grade A");
} else if (score >= 70) {
    System.out.println("Grade B");
} else {
    System.out.println("Keep practising");
}

Java tests conditions from top to bottom. Once a branch matches, its block runs and the remaining branches are skipped. Put more specific or higher-threshold conditions first when order matters.

switch#

A switch can be clearer when choosing between known values:

int day = 2;

switch (day) {
    case 1 -> System.out.println("Monday");
    case 2 -> System.out.println("Tuesday");
    case 3 -> System.out.println("Wednesday");
    default -> System.out.println("Another day");
}

This arrow-style syntax is available in modern Java versions. In older Java versions, use the traditional case and break form supported by that version.

Common mistakes#

• Using = instead of == when comparing primitive values. Assignment and comparison are different operations.
• Forgetting braces around multi-statement branches.
• Testing a broad condition before a more specific condition, making the latter unreachable.
• Comparing strings with == when you intend to compare their contents; use .equals() instead.

Practice#

Create an integer temperature. Print “Cold” below 15, “Comfortable” from 15 through 25, and “Hot” above 25. Test boundary values such as 15 and 25.