import java.util.HashMap; import java.util.Map; import java.util.Scanner; class GradeQuerySystem {     private Map gradeBook;     public GradeQuerySystem() {         gradeBook = new HashMap();     }     public void addStudentGrade(String studentName, int grade) {         gradeBook.put(studentName, grade);     }     public int getStudentGrade(String studentName) {         if (gradeBook.containsKey(studentName)) {             return gradeBook.get(studentName);         } else {             return -1; // 表示找不到该学生的成绩         }     } } public class Main {     public static void main(String[] args) {         GradeQuerySystem system = new GradeQuerySystem();         system.addStudentGrade("Alice", 85);         system.addStudentGrade("Bob", 92);         system.addStudentGrade("Charlie", 78);         system.addStudentGrade("David", 95);         system.addStudentGrade("Eve", 88);         Scanner scanner = new Scanner(System.in);         System.out.print("请输入学生姓名：");         String studentName = scanner.nextLine();         int grade = system.getStudentGrade(studentName);         if (grade != -1) {             System.out.println(studentName + "的成绩为：" + grade);         } else {             System.out.println("找不到该学生的成绩！");         }     } } 学生成绩查询系统是现代教育管理中不可或缺的一部分。通过使用学生成绩查询系统，老师可以方便地管理和查询学生的学业成绩，为学生提供个性化的学术指导。