Switch Statements

A switch statement is another way to make decisions in Java, and is often a cleaner alternative to a long chain of else if statements when you're comparing a single variable against many possible values.

Switch Formula

Show code

switch ([variable]) {
    case [value1]:
        [code to run]
        break;
    case [value2]:
        [code to run]
        break;
    default:
        [code to run if no case matches]
}

Show code

int allianceStation = 2;

switch (allianceStation) {
    case 1:
        System.out.println("Station 1");
        break;
    case 2:
        System.out.println("Station 2");
        break;
    case 3:
        System.out.println("Station 3");
        break;
    default:
        System.out.println("Invalid station");
}

Output:

Station 2

Comparing to an if-else Chain

The switch statement above is functionally equivalent to the following else if chain, but is arguably easier to read when there are many possible values to check:

if (allianceStation == 1) {
    System.out.println("Station 1");
} else if (allianceStation == 2) {
    System.out.println("Station 2");
} else if (allianceStation == 3) {
    System.out.println("Station 3");
} else {
    System.out.println("Invalid station");
}

Fall-Through

Each case in a switch statement needs a break statement to stop execution from "falling through" into the next case. Without break, Java will keep running code downward through every subsequent case until it hits a break or reaches the end of the switch block.

Show code

int allianceStation = 1;

switch (allianceStation) {
    case 1:
        System.out.println("Station 1");
    case 2:
        System.out.println("Station 2");
        break;
    default:
        System.out.println("Invalid station");
}

Output:

Station 1
Station 2

Even though allianceStation was 1, both "Station 1" and "Station 2" were printed, since there was no break after the first case. Forgetting a break is one of the most common switch statement bugs, so it's important to always double check your cases.

The default Case

The default case runs when none of the other cases match the variable's value. It's similar to the final else in an if-else if-else chain, and while it isn't required, it's good practice to include one to handle unexpected values.

Modern Switch Expressions

Newer versions of Java support a more concise "arrow" syntax for switch statements, which doesn't require break statements, since each case only runs its own code by default (no fall-through).

switch (allianceStation) {
    case 1 -> System.out.println("Station 1");
    case 2 -> System.out.println("Station 2");
    case 3 -> System.out.println("Station 3");
    default -> System.out.println("Invalid station");
}

This syntax is generally preferred in modern Java code, since it's more concise and eliminates the risk of accidental fall-through entirely.