class RecursiveCollectionLineAggregator<T> implements LineAggregator<Collection<T>> {

	private static final String LINE_SEPARATOR = System.getProperty("line.separator");

	private LineAggregator<T> delegate = new PassThroughLineAggregator<>();

	/**
	 * Public setter for the {@link LineAggregator} to use on single items, that are not
	 * Strings. This can be used to strategise the conversion of collection and array
	 * elements to a String.<br>
	 * @param delegate the line aggregator to set. Defaults to a pass through.
	 */
	public void setDelegate(LineAggregator<T> delegate) {
		this.delegate = delegate;
	}

	@Override
	public String aggregate(Collection<T> items) {<FILL_FUNCTION_BODY>}

}

		StringBuilder builder = new StringBuilder();
		for (T value : items) {
			builder.append(delegate.aggregate(value)).append(LINE_SEPARATOR);
		}
		return builder.delete(builder.length() - LINE_SEPARATOR.length(), builder.length()).toString();
	
<no_super_class>