代码

import java.util.*;
class ScoreRecord {private String studentId;private String name;private String subject;private int score;public ScoreRecord(String studentId, String name, String subject, int score) {this.studentId = studentId;this.name = name;this.subject = subject;this.score = score;}public String getStudentId() { return studentId; }public String getName() { return name; }public String getSubject() { return subject; }public int getScore() { return score; }
}public class StudentScoreAnalysis_NoStream {public static void main(String[] args) {String[] scores = {"S1001,张三,数学,95","S1002,李四,数学,76","S1003,王五,数学,59","S1001,张三,英语,88","S1002,李四,英语,90","S1003,王五,英语,66","S1001,张三,物理,91","S1002,李四,物理,54","S1003,王五,物理,73","S1004,赵六,数学,88","S1004,赵六,英语,92","S1004,赵六,物理,85"};// 0. 构造ScoreRecord集合List<ScoreRecord> recordList = new ArrayList<>();for (int i = 0; i < scores.length; i++) {String[] parts = scores[i].split(",");recordList.add(new ScoreRecord(parts[0], parts[1], parts[2], Integer.parseInt(parts[3])));}// 1. 列出所有学生姓名System.out.println("-------------------");Set<String> studentNames = new TreeSet<>();for (ScoreRecord r : recordList) {studentNames.add(r.getName());}System.out.println("列出所有学生姓名 : " + studentNames);// 2. 每个学生总分System.out.println("-------------------");Map<String, Integer> totalScores = new HashMap<>();for (ScoreRecord r : recordList) {if(totalScores.containsKey(r.getName())){int currentScore = totalScores.get(r.getName());currentScore+=r.getScore();totalScores.put(r.getName(),currentScore);}else {totalScores.put(r.getName(),r.getScore());}}System.out.println("每个学生总分");for (Map.Entry<String, Integer> e : totalScores.entrySet()) {System.out.println(e.getKey()+":"+e.getValue());}// 找出总分最高学生System.out.println("-------------------");String topStudent = "";int maxTotal = Integer.MIN_VALUE;for (Map.Entry<String, Integer> e : totalScores.entrySet()) {if (e.getValue() > maxTotal) {maxTotal = e.getValue();topStudent = e.getKey();}}System.out.println("总分最高学生: " + topStudent + " (" + maxTotal + ")");// 6. 每个学生平均分System.out.println("-------------------");Map<String, Integer> sumScores = new HashMap<>();Map<String, Integer> countScores = new HashMap<>();for (ScoreRecord r : recordList) {sumScores.put(r.getName(), sumScores.getOrDefault(r.getName(), 0) + r.getScore());countScores.put(r.getName(), countScores.getOrDefault(r.getName(), 0) + 1);}for (String name : sumScores.keySet()) {double avg = sumScores.get(name) * 1.0 / countScores.get(name);System.out.printf("%s: %.2f%n", name, avg);}// 5. 不及格学生记录System.out.println("-------------------");System.out.println("不及格记录:");for (ScoreRecord r : recordList) {if (r.getScore() < 60) {System.out.println(r.getName() + " - " + r.getSubject() + ": " + r.getScore());}}// 3. 每门课程的最高分System.out.println("-------------------");Map<String, ScoreRecord> subjectTop = new HashMap<>();for (ScoreRecord r : recordList) {if (!subjectTop.containsKey(r.getSubject()) ||r.getScore() > subjectTop.get(r.getSubject()).getScore()) {subjectTop.put(r.getSubject(), r);}}System.out.println("每门课程的最高分:");for (String subject : subjectTop.keySet()) {ScoreRecord rec = subjectTop.get(subject);System.out.println(subject + ": " + rec.getName() + " (" + rec.getScore() + ")");}// 7. 每门课程平均分System.out.println("-------------------");System.out.println("每门课程平均分:");Map<String, Integer> subjectSum = new HashMap<>();Map<String, Integer> subjectCount = new HashMap<>();for (ScoreRecord r : recordList) {subjectSum.put(r.getSubject(), subjectSum.getOrDefault(r.getSubject(), 0) + r.getScore());subjectCount.put(r.getSubject(), subjectCount.getOrDefault(r.getSubject(), 0) + 1);}for (String subject : subjectSum.keySet()) {double avg = subjectSum.get(subject) * 1.0 / subjectCount.get(subject);System.out.printf("%s: %.2f%n", subject, avg);}// 8. 平均分最高课程System.out.println("-------------------");String topSubject = "";double highestAvg = Double.MIN_VALUE;for (String subject : subjectSum.keySet()) {double avg = subjectSum.get(subject) * 1.0 / subjectCount.get(subject);if (avg > highestAvg) {highestAvg = avg;topSubject = subject;}}System.out.println("平均分最高课程: " + topSubject);// 10. 成绩明细表System.out.println("-------------------");System.out.println("成绩明细表:");Map<String, List<ScoreRecord>> byStudent = new LinkedHashMap<>();for (ScoreRecord r : recordList) {if (!byStudent.containsKey(r.getName())) {byStudent.put(r.getName(), new ArrayList<>());}byStudent.get(r.getName()).add(r);}for (String name : byStudent.keySet()) {System.out.print(name + ": ");List<ScoreRecord> list = byStudent.get(name);for (ScoreRecord r : list) {System.out.print(r.getSubject() + "(" + r.getScore() + ") ");}System.out.println();}}
}

输出

-------------------
列出所有学生姓名 : [张三, 李四, 王五, 赵六]
-------------------
每个学生总分
李四:220
张三:274
王五:198
赵六:265
-------------------
总分最高学生: 张三 (274)
-------------------
李四: 73.33
张三: 91.33
王五: 66.00
赵六: 88.33
-------------------
不及格记录:
王五 - 数学: 59
李四 - 物理: 54
-------------------
每门课程的最高分:
物理: 张三 (91)
数学: 张三 (95)
英语: 赵六 (92)
-------------------
每门课程平均分:
物理: 75.75
数学: 79.50
英语: 84.00
-------------------
平均分最高课程: 英语
-------------------
成绩明细表:
张三: 数学(95) 英语(88) 物理(91) 
李四: 数学(76) 英语(90) 物理(54) 
王五: 数学(59) 英语(66) 物理(73) 
赵六: 数学(88) 英语(92) 物理(85)