convert vector to list

Question

How to convert a vector to a list?

Answer 1

If you want a utility method that converts an generic Vector type to an appropriate ArrayList, you could use the following:

public static  ArrayList toList(Vector source) {
    return new ArrayList(source);
}

In your code, you would use the utility method as follows:

public void myCode() {
    List items = toList(someVector);
    System.out.println("items => " + items);
}

You can also use the built-in java.util.Collections.list(Enumeration) as follows:

public void myMethod() {
    Vector stringVector = new Vector();
    List theList = Collections.list(stringVector.elements());
    System.out.println("theList => " + theList);
}

But like someone mentioned below, a Vector is-a List! So why would you need to do this? Perhaps you don't want some code you use to know it's working with a Vector - perhaps it is inappropriately down-casting and you wish to eliminate this code-smell. You could then use

// the method i give my Vector to can't cast it to Vector
methodThatUsesList( Collections.unmodifiableList(theVector) );

if the List should be modified. An off-the-cuff mutable wrapper is:

public static  List asList(final List vector) {
    return new AbstractList() {
        public E get(int index) { return vector.get(index); }
        public int size() { return vector.size(); }
        public E set(int index, E element) { return vector.set(index, element); }
        public void add(int index, E element) { vector.add(index, element); }
        public E remove(int index) { return vector.remove(index); }
    }
}