Function with multiple outputs in Java

Question

How to create a JAVA function with multiple outputs? Something like:

private (ArrayList<Integer[]>, int indexes) sortObjects(ArrayList<Integer[]> arr) {
//...
}

What do you mean by multiple outputs? Are you referring to the return values? If this is the case, you should create a new class instead, and put your arraylist, int indexes and whatever else you want in there. Then modify the function to return your newly created class. — Manish, Jan 03 '12 at 10:11

score 5 · Answer 1 · answered Jan 03 '12 at 10:08

5

Java's not like Python - no tuples. You have to create an Object and wrap all your outputs into it. Another solution might be a Collection of some sort, but I think the former means better encapsulation.

answered Jan 03 '12 at 10:08

duffymo

305,152
44
369
561

1

Ouh, examples are here: http://stackoverflow.com/questions/457629/how-to-return-multiple-objects-from-a-java-method – Klausos Klausos Jan 03 '12 at 10:11

score 2 · Answer 2 · answered Jan 03 '12 at 10:57

In some cases it is possible to use method arguments to handle result values. In your case, part of the result is a list (which may be updated destructively). So you could change your method-signature to the following form:

private int sortObjects(ArrayList<Integer[]> input, ArrayList<Integer[]> result) {
   int res = 0;
   for (Integer[] ints : input) {
     if (condition(ints) {
       result.add(calculatedValue);
       res++
     }
   }
   return res;
}

score 1 · Answer 3 · answered Jan 03 '12 at 10:08

1

You cannot, you can either

Create a wrapper return object
Create multiple functions

answered Jan 03 '12 at 10:08

Johan Sjöberg

47,929
21
130
148

score 1 · Answer 4 · answered Jan 03 '12 at 10:09

1

Use an object as return value.

class SortedObjects { private ArrayList<Integer[]> _first; int _indexes; ...getter/setter/ctor... }

private SortedObjects sortObjects(ArrayList<Integer[]> arr) { ... }

answered Jan 03 '12 at 10:09

Matten

17,365
2
42
64

score 1 · Answer 5 · answered Jan 03 '12 at 10:09

1

You cannot.

The simple solution is to return an array of objects. A more robust solution is to create a class for holding the response, and use getters to get the individual values from the response object returned by your code.

answered Jan 03 '12 at 10:09

Thorbjørn Ravn Andersen

73,784
33
194
347

score 1 · Answer 6 · answered Jan 03 '12 at 10:09

1

You have to create a class which includes member variables for each piece of information you require, and return an object of that class.

answered Jan 03 '12 at 10:09

James McLeod

2,381
1
17
19

score 1 · Answer 7 · answered Jan 03 '12 at 10:23

Another approach is to use an Object which wraps the collection.

class SortableCollection {
    final List<Integer[]> tables = ...
    int indexes = -1;

    public void sortObjects() {
        // perform sort on tables.
        indexes = ...
    }
}

As it operates on a mutable object, there is no arguments or return values.

Function with multiple outputs in Java

7 Answers7