Remove all instances of an element from a collection

I need to remove all elements from a collection c that are less than a given object.

The signature should be void removeLess(Collection c, Object o)

Would something like this work?:

vo开发者_如何学Goid removeLess(Collection c, Object o) {
    Iterator<Integer> itr = c.iterator();
    while (itr.hasNext()) {
        if (itr.next.compareTo(o) < 0) {
            c.remove(o);
        }
    }
}

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You can't use c.remove(o) or you invalidate the iterator; but you can use the optional method Iterator.remove(), as in itr.remove(). It removes the last object returned from "next".

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It looks like it would, provided that the Collection class's Iterator supports the remove method.

And you have a syntax error - should be itr.next().

Also, try it?

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No, it won't work since you can't modify a collection while there is an Iterator over it. You should accumulate elements that you will remove into another temporary collection and remove them all afterwards.

A better approach, if you don't care about the indices in which the element reside, would be to use the TreeSet<T> class which, by structure, provides the method tailSet(T element) which does exactly what you need.

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You would have to use the Iterator's remove method instead, and the signature would need to be:

<E extends Comparable<? super E>> void removeLess(Collection<E> c, E o)

With a NavigableSet<E> such as a TreeSet, you could just do:

set.headSet(o).clear();