CODEWITHSUNDEEP
javaswitch-statementcase
M. Ruiz
M. Ruiz

Reputation: 65

Is there a way to have an option that can run all previous cases in a switch statement?

For example, if the user selects option 1 - 3 it does their own specific task. If user enters 4, it does all options 1 - 3. Is there a way to accomplish this using switch statement without having to copy and paste all code from each of the cases?

switch (option) {
    case 1: {
        System.out.println("1");
        break;
    }
    case 2: {
        System.out.println("2");
        break;
    }
    case 3: {
        System.out.println("3");
        break;
    }
    case 4: {
        System.out.println("1");
        System.out.println("2");
        System.out.println("3");
        break;
    }
    default: {
        System.out.print("Invalid selection.");
        break;
    }
}

Upvotes: 0

Views: 257

Answers (1)

Nowhere Man
Nowhere Man

Reputation: 19545

switch statement does not allow repeated case's, so requested functionality may be achieved only with multiple if statements using OR operation:

if (option == 1 || option == 4) {
    System.out.println("1");
}
if (option == 2 || option == 4) {
    System.out.println("2");
}
if (option == 3 || option == 4) {
    System.out.println("3");
}

Another approach could consist in preparing a map of options to certain actions or lists of actions to implement required logic.

  1. Map<Integer, Runnable> + Predicate.or
// define a map of simple actions
static final Map<Integer, Runnable> actionMap = new LinkedHashMap<>(); 
static {
    actionMap.put(1, ()-> System.out.println("1"));
    actionMap.put(2, ()-> System.out.println("2"));
    actionMap.put(3, ()-> System.out.println("3"));
};

public static void runOption(Integer option) {
    if (option < 1 || option > 4) {
        System.out.println("No action found for option = " + option);
    } else {
        Predicate<Integer> is4 = (x) -> 4 == option;
        
        actionMap.keySet()
            .stream()
            .filter(is4.or(option::equals))
            .map(actionMap::get)
            .forEach(Runnable::run);
    }
}

Test:

IntStream.range(0, 6).boxed().forEach(MyClass::runOption);

Output:

No action found for option = 0
1
2
3
1
2
3
No action found for option = 5
  1. Map<Integer, List<Runnable>> with getOrDefault

This method facilitates any composition of actions, not only having one action to run all available actions.

static Runnable 
    action1 = ()-> System.out.println("1"),
    action2 = ()-> System.out.println("2"),
    action3 = ()-> System.out.println("3");

static final Map<Integer, List<Runnable>> actionListMap = Map.of(
    1, Arrays.asList(action1),
    2, Arrays.asList(action2),
    3, Arrays.asList(action3),
    4, Arrays.asList(action1, action2, action3)
);

public static void runOptionList(Integer option) {
    actionListMap.getOrDefault(
        option, 
        Arrays.asList(() -> System.out.println("No action found for option = " + option))
    )
    .forEach(Runnable::run);
}

Upvotes: 4

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