ADD file via upload

src/MathProblemGenerator.java

@@ -0,0 +1,10 @@
+// Makeproblem.java
+/**
+ * 数学题目生成器接口。
+ */
+public interface MathProblemGenerator {
+  String generateSmartExpression();
+  String buildExpression(int operatorCount, int complexityTarget);
+  String generateSimpleExpression(int advancedOperationTarget);
+  char getRandomOperator(String availableOperators);
+}