I have to disagree here. It would just be boilerplate. It would look like this:

	private String[] cachedReturnArray

	private String[] getReturnArray() {
		if (cachedReturnArray != null) {
			return cachedReturnArray
		}
		assert originalRow != null
		int outputSize = originalRow.size() + transformedColumnsIndexes.size()
		cachedReturnArray = new String[outputSize]
	}

This would only be simpler to someone who doesn't know about `@Lazy`. Otherwise it's a boilerplate field and null check.