private void verifyInput(final List<AbstractNode> initialGrammar) throws InterruptedException {
for (AbstractNode node : initialGrammar) {
if (Thread.interrupted()) {
throw new InterruptedException();
}
if (!NodeType.ELEMENT.equals(node.getType())) {
final StringBuilder sb = new StringBuilder("Initial grammar contains rule with ");
sb.append(node.getType().toString());
sb.append(" as left side.");
throw new IllegalArgumentException(sb.toString());
}
if (node == null) {
throw new IllegalArgumentException("Got null as left side in grammar.");
}
}
}
