Best way to get value from Collection by index

Question

What is the best way to get value from java.util.Collection by index?

Answer 1

You shouldn't. a Collection avoids talking about indexes specifically because it might not make sense for the specific collection. For example, a List implies some form of ordering, but a Set does not.

Collection<String> myCollection = new HashSet<String>(); myCollection.add("Hello"); myCollection.add("World");  for (String elem : myCollection) {     System.out.println("elem = " + elem); }  System.out.println("myCollection.toArray()[0] = " + myCollection.toArray()[0]); 

gives me:

elem = World elem = Hello myCollection.toArray()[0] = World 

whilst:

myCollection = new ArrayList<String>(); myCollection.add("Hello"); myCollection.add("World");  for (String elem : myCollection) {     System.out.println("elem = " + elem); }  System.out.println("myCollection.toArray()[0] = " + myCollection.toArray()[0]); 

gives me:

elem = Hello elem = World myCollection.toArray()[0] = Hello 

Why do you want to do this? Could you not just iterate over the collection?