update:demo3

com/study/demo3/StudentManager.java

@@ -0,0 +1,28 @@
+package com.study.demo3;
+import java.util.*;
+
+public class StudentManager {
+    public static void main(String[] args) {
+        List<String> studentNames = new ArrayList<>();
+        Map<String, Integer> studentScores = new HashMap<>();
+
+        studentNames.add("张三");
+        studentNames.add("李四");
+        studentNames.add("王五");
+
+        studentScores.put("张三", 85);
+        studentScores.put("李四", 77);
+        studentScores.put("王五", 99);
+
+        System.out.println("--- 所有学生姓名 ---");
+        for (String name : studentNames) {
+            System.out.println(name);
+        }
+
+        studentScores.put("张三", 70);
+
+        Integer zhangsanScore = studentScores.get("张三");
+        System.out.println("\n--- 修改后张三的成绩 ---");
+        System.out.println("张三的成绩: " + zhangsanScore);
+    }
+}