Is there a Union in Java Generics?

Question

Can I contain two different types in a collection? For example, can I have List< String U Integer > ?

Answer 1

Nope. You have a couple of alternatives, though:

• You can use a List < Object > and stash whatever you like; or

• You can use a List < Class-with-2-members > and put your data in one of those class members.

EDIT: Example.

class UnionHolder {
  public String stringValue;
  public int intValue;
}

List < UnionHolder > myList 
...

Of course you'll need a bit of additional code to figure out which kind of data to pull out of the UnionHolder object you just got out of your list. One possibility would be to have a 3rd member which has different values depending on which it is, or you could, say, have a member function like

public boolean isItAString() { return (this.stringValue != null }