diff --git a/src/QuestionGenerator.java b/src/QuestionGenerator.java
new file mode 100644
index 0000000..3e89dad
--- /dev/null
+++ b/src/QuestionGenerator.java
@@ -0,0 +1,6 @@
+public interface QuestionGenerator {
+	String generateQuestion();
+	String normalizeQuestion(String question);
+	String generateOperator(String[] operators);
+	boolean isValidParentheses(String expression);
+}