update:demo2

com/study/demo2/Student.java

@@ -0,0 +1,40 @@
+package com.study.demo2;
+
+public class Student {
+    private String id;
+    private String name;
+    private int[] score = new int[10];
+
+    public Student(String id, String name, int[] scores) {
+        this.id = id;
+        this.name = name;
+        if (scores.length == 10) {
+            this.score = scores;
+        }
+    }
+
+    public double getAverage() {
+        int sum = 0;
+        for (int s : score) {
+            sum += s;
+        }
+        return (double) Math.round((sum / 10.0) * 100) / 100;
+    }
+
+    public int getMaxScore() {
+        int max = score[0];
+        for (int s : score) {
+            if (s > max) max = s;
+        }
+        return max;
+    }
+
+    public char getGrade() {
+        double avg = getAverage();
+        if (avg >= 90) return 'A';
+        else if (avg >= 80) return 'B';
+        else if (avg >= 70) return 'C';
+        else if (avg >= 60) return 'D';
+        else return 'E';
+    }
+}