How to return multiple objects from a Java method?

java return
Jagmal picture Jagmal · Jan 19, 2009 · Viewed 238.2k times · Source

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 (since the two Objects are related) or return an ArrayList of Object objects.

To be more precise, the two objects I want to return are (a) List of objects and (b) comma separated names of the same.

I want to return these two Objects from one method because I dont want to iterate through the list of objects to get the comma separated names (which I can do in the same loop in this method).

Somehow, returning a HashMap does not look a very elegant way of doing so.

Answer

Joachim Sauer picture Joachim Sauer · Jan 19, 2009

If you want to return two objects you usually want to return a single object that encapsulates the two objects instead.

You could return a List of NamedObject objects like this:

public class NamedObject<T> {
  public final String name;
  public final T object;

  public NamedObject(String name, T object) {
    this.name = name;
    this.object = object;
  }
}

Then you can easily return a List<NamedObject<WhateverTypeYouWant>>.

Also: Why would you want to return a comma-separated list of names instead of a List<String>? Or better yet, return a Map<String,TheObjectType> with the keys being the names and the values the objects (unless your objects have specified order, in which case a NavigableMap might be what you want.

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