diff --git a/MathProblemGenerator.java b/MathProblemGenerator.java
new file mode 100644
index 0000000..3a65350
--- /dev/null
+++ b/MathProblemGenerator.java
@@ -0,0 +1,34 @@
+import java.text.DecimalFormat;
+import java.util.Random;
+
+/**
+ * 数学题目生成器，根据不同难度生成相应的数学题目（外观类）
+ * 将具体生成逻辑委托给对应子类，保持对外 API 不变。
+ */
+public class MathProblemGenerator {
+    private final Random random;
+    private final DecimalFormat df;
+
+    public MathProblemGenerator() {
+        this.random = new Random();
+        this.df = new DecimalFormat("#.##");
+    }
+
+    /**
+     * 根据难度生成数学题目
+     * @param difficulty 难度级别（小学、初中、高中）
+     * @return 生成的数学题目
+     */
+    public MathProblem generateProblem(String difficulty) {
+        switch (difficulty) {
+            case "小学":
+                return new ElementaryProblemGenerator(random, df).generate();
+            case "初中":
+                return new MiddleSchoolProblemGenerator(random, df).generate();
+            case "高中":
+                return new HighSchoolProblemGenerator(random, df).generate();
+            default:
+                throw new IllegalArgumentException("不支持的难度级别: " + difficulty);
+        }
+    }
+}
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