How to return multiple objects from a Java method?

Question

I want to return two objects from a Java method and was wondering what could be a good way of doing so?

The possible ways I can think of are: return a HashMap<

Answer 1

I followed a similar approach than the described in the other answers with a few tweaks based on the requirement I had, basically I created the following classes(Just in case, everything is Java):

public class Pair {
    final L left;
    final R right;

    public Pair(L left, R right) {
        this.left = left;
        this.right = right;
    }

    public  T get(Class param) {
        return (T) (param == this.left.getClass() ? this.left : this.right);
    }

    public static  Pair of(L left, R right) {
        return new Pair(left, right);
    }
}

Then, my requirement was simple, in the repository Class that reaches the DB, for the Get Methods than retrieve data from the DB, I need to check if it failed or succeed, then, if succeed, I needed to play with the returning list, if failed, stop the execution and notify the error.

So, for example, my methods are like this:

public Pair> getCustomers() {
    List list = new ArrayList();
    try {
    /*
    * Do some work to get the list of Customers from the DB
    * */
    } catch (SQLException e) {
        return Pair.of(
                       new ResultMessage(e.getErrorCode(), e.getMessage()), // Left 
                       null);  // Right
    }
    return Pair.of(
                   new ResultMessage(0, "SUCCESS"), // Left 
                   list); // Right
}

Where ResultMessage is just a class with two fields (code/message) and Customer is any class with a bunch of fields that comes from the DB.

Then, to check the result I just do this:

void doSomething(){
    Pair> customerResult = _repository.getCustomers();
    if (customerResult.get(ResultMessage.class).getCode() == 0) {
        List listOfCustomers = customerResult.get(List.class);
        System.out.println("do SOMETHING with the list ;) ");
    }else {
        System.out.println("Raised Error... do nothing!");
    }
}