elk-util-parent/elk-util-collections/src/main/java/org/semanticweb/elk/util/collections/Operations.java
public static <T> void dumpDiff(Collection<T> first, Collection<T> second,
			Writer writer, String prefix) throws IOException {
		for (T element : first)
			if (!second.contains(element))
				writer.append(prefix + element + "\n");
	}
public static <T> void dumpDiff(Collection<T> first, Collection<T> second,
			Writer writer, String prefix) throws IOException {
		for (T element : first)
			if (!second.contains(element))
				writer.append(prefix + element + "\n");
	}
Prints the elements present in the first {@link Collection} but not in
the second {@link Collection} using the given {@link Writer} and
prefixing all messages with a given prefix.

@param first
@param second
@param writer
@param prefix
@throws IOException