Convert Collection to List

Question

Hello, I want to say how to convert a Collection to a List in Java

Answer 1

Collection<MyObjectType> myCollection = ...;
List<MyObjectType> list = new ArrayList<MyObjectType>(myCollection);

See the Collections trail in the Java tutorials.

Answer 2

Make a new list, and call addAll with the Collection.

Answer 3

If you have already created an instance of your List subtype (e.g., ArrayList, LinkedList), you could use the addAll method.

e.g.,

l.addAll(myCollection)

Many list subtypes can also take the source collection in their constructor.

Answer 4

How do you initialise a Collection collection ..?

Answer 5

you can use either of the 2 solutions .. but think about whether it is necessary to clone your collections, since both the collections will contain the same object references

Answer 6

Collection and List are interfaces. You can take any Implementation of the List interface: ArrayList LinkedList and just cast it back to a Collection because it is at the Top

Example below shows casting from ArrayList

public static void main (String args[]) {
    Collection c = getCollection();
    List myList = (ArrayList) c;
}

public static Collection getCollection()
{
    Collection c = new ArrayList();
    c.add("Apple");
    c.add("Oranges");
    return c;
}