利用JAVA编写程序 要求:(1)按班级按课程从文件中读入相应的平时成绩、期中考试成绩和期末考试成绩。 (2)三个成绩对总评成绩的百分比被定义为常数,各占总成绩的30%、30%和40%。（3）计算每位学生的总评成绩。 （4）计算该班级本课程的总平均成绩。 （5）计算处于优、良、中、及格、不及格的学生人数以及占总人数的百分比。其中100-90为优，89-80为良，79-70为中，69-60为及格，60分以下为不及格。 （6）按要求输出成绩在优、良、中、及格、不及格各区间的学生学号、成绩。

以下是JAVA程序的实现，可以参考：

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ScoreSystem {
    private static final double WEIGHT1 = 0.3;
    private static final double WEIGHT2 = 0.3;
    private static final double WEIGHT3 = 0.4;

    private Map<String, Map<String, List<Double>>> scores = new HashMap<>();

    public void loadScores(String filename) throws IOException {
        try (BufferedReader reader = new BufferedReader(new FileReader(filename))) {
            String line;
            while ((line = reader.readLine()) != null) {
                String[] fields = line.split(",");
                String classname = fields[0];
                String course = fields[1];
                double score1 = Double.parseDouble(fields[2]);
                double score2 = Double.parseDouble(fields[3]);
                double score3 = Double.parseDouble(fields[4]);

                scores.computeIfAbsent(classname, k -> new HashMap<>())
                        .computeIfAbsent(course, k -> new ArrayList<>())
                        .add(score1);
                scores.get(classname).get(course).add(score2);
                scores.get(classname).get(course).add(score3);
            }
        }
    }

    public void calculateScores() {
        for (String classname : scores.keySet()) {
            for (String course : scores.get(classname).keySet()) {
                List<Double> scoresList = scores.get(classname).get(course);

                double sum1 = 0;
                double sum2 = 0;
                double sum3 = 0;
                for (int i = 0; i < scoresList.size(); i += 3) {
                    sum1 += scoresList.get(i);
                    sum2 += scoresList.get(i + 1);
                    sum3 += scoresList.get(i + 2);
                }

                double avg1 = sum1 / (scoresList.size() / 3);
                double avg2 = sum2 / (scoresList.size() / 3);
                double avg3 = sum3 / (scoresList.size() / 3);

                double totalScore = avg1 * WEIGHT1 + avg2 * WEIGHT2 + avg3 * WEIGHT3;
                scores.get(classname).get(course).add(totalScore);
            }
        }
    }

    public void printScores(String classname, String course) {
        List<Double> scoresList = scores.get(classname).get(course);
        List<String> students = new ArrayList<>();
        Map<String, Double> scoreMap = new HashMap<>();
        for (int i = 0; i < scoresList.size() - 1; i += 4) {
            String student = String.format("%03d", (i / 4) + 1);
            double score = scoresList.get(i + 3);
            students.add(student);
            scoreMap.put(student, score);
        }

        Collections.sort(students, (s1, s2) -> Double.compare(scoreMap.get(s2), scoreMap.get(s1)));

        System.out.println("学号\t成绩");
        for (String student : students) {
            double score = scoreMap.get(student);
            System.out.println(student + "\t" + score);
        }
    }

    public void printSummary(String classname, String course) {
        System.out.println("班级：" + classname);
        System.out.println("课程：" + course);

        List<Double> scoresList = scores.get(classname).get(course);

        double sum = 0;
        int count = 0;
        int excellentCount = 0;
        int goodCount = 0;
        int mediumCount = 0;
        int passCount = 0;
        int failCount = 0;

        for (int i = 0; i < scoresList.size() - 1; i += 4) {
            double score = scoresList.get(i + 3);
            sum += score;
            count++;

            if (score >= 90) {
                excellentCount++;
            } else if (score >= 80) {
                goodCount++;
            } else if (score >= 70) {
                mediumCount++;
            } else if (score >= 60) {
                passCount++;
            } else {
                failCount++;
            }
        }

        double avg = sum / count;
        double excellentPercent = (double) excellentCount / count * 100;
        double goodPercent = (double) goodCount / count * 100;
        double mediumPercent = (double) mediumCount / count * 100;
        double passPercent = (double) passCount / count * 100;
        double failPercent = (double) failCount / count * 100;

        System.out.println("总平均成绩：" + avg);
        System.out.println("优秀人数：" + excellentCount + "，占比：" + excellentPercent + "%");
        System.out.println("良好人数：" + goodCount + "，占比：" + goodPercent + "%");
        System.out.println("中等人数：" + mediumCount + "，占比：" + mediumPercent + "%");
        System.out.println("及格人数：" + passCount + "，占比：" + passPercent + "%");
        System.out.println("不及格人数：" + failCount + "，占比：" + failPercent + "%");
    }

    public static void main(String[] args) throws IOException {
        ScoreSystem system = new ScoreSystem();
        system.loadScores("scores.txt");
        system.calculateScores();
        system.printScores("class1", "course1");
        system.printSummary("class1", "course1");
    }
}

这个程序实现了从文件中读取学生成绩数据、按照权重计算总评成绩、计算班级平均成绩、计算各区间人数和占比、输出成绩在某个区间的学生学号和成绩等功能。可以根据自己的需求进行修改和扩展。