java.输入5个学生的信息（包含学号、姓名、3科成绩），统计各学生的总分，然后将学生信息和统计结果存入二进制数据文件STUDENT.DAT中。 从第（9）题中建立的STUDENT.DAT文件中读取数据，寻找平均分最高的学生，并输出该学生的所有信息

好的，这是一个关于学生信息的问题，需要用到Java语言来编写程序。首先，我们需要定义一个学生类，包含学号、姓名和3科成绩，然后定义一个函数来读取5个学生的信息，并计算每个学生的总分，最后将学生信息和统计结果存入二进制数据文件STUDENT.DAT中。代码如下：

import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public class Student {
    private String id;
    private String name;
    private float score1;
    private float score2;
    private float score3;
    private float total;

    public Student(String id, String name, float score1, float score2, float score3) {
        this.id = id;
        this.name = name;
        this.score1 = score1;
        this.score2 = score2;
        this.score3 = score3;
        this.total = score1 + score2 + score3;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public float getScore1() {
        return score1;
    }

    public float getScore2() {
        return score2;
    }

    public float getScore3() {
        return score3;
    }

    public float getTotal() {
        return total;
    }

    public static void main(String[] args) {
        Student[] students = readStudents();
        writeStudents(students);
        students = readStudentData();
        Student maxStudent = findMaxAverage(students);
        System.out.println("平均分最高的学生信息如下：");
        System.out.println("学号：" + maxStudent.getId());
        System.out.println("姓名：" + maxStudent.getName());
        System.out.println("第1科成绩：" + maxStudent.getScore1());
        System.out.println("第2科成绩：" + maxStudent.getScore2());
        System.out.println("第3科成绩：" + maxStudent.getScore3());
        System.out.println("总分：" + maxStudent.getTotal());
        System.out.println("平均分：" + (maxStudent.getTotal() / 3));
    }

    private static Student[] readStudents() {
        Student[] students = new Student[5];
        for (int i = 0; i < 5; i++) {
            String id = System.console().readLine("请输入第" + (i + 1) + "个学生的学号：");
            String name = System.console().readLine("请输入第" + (i + 1) + "个学生的姓名：");
            float score1 = Float.parseFloat(System.console().readLine("请输入第" + (i + 1) + "个学生的第1科成绩："));
            float score2 = Float.parseFloat(System.console().readLine("请输入第" + (i + 1) + "个学生的第2科成绩："));
            float score3 = Float.parseFloat(System.console().readLine("请输入第" + (i + 1) + "个学生的第3科成绩："));
            Student student = new Student(id, name, score1, score2, score3);
            students[i] = student;
        }
        return students;
    }

    private static void writeStudents(Student[] students) {
        try (DataOutputStream out = new DataOutputStream(new FileOutputStream("STUDENT.DAT"))) {
            for (Student student : students) {
                out.writeUTF(student.getId());
                out.writeUTF(student.getName());
                out.writeFloat(student.getScore1());
                out.writeFloat(student.getScore2());
                out.writeFloat(student.getScore3());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static Student[] readStudentData() {
        Student[] students = new Student[5];
        try {
            byte[] data = Files.readAllBytes(Paths.get("STUDENT.DAT"));
            for (int i = 0; i < 5; i++) {
                int offset = i * 22;
                String id = new String(data, offset, 5, "UTF-8").trim();
                String name = new String(data, offset + 5, 20, "UTF-8").trim();
                float score1 = Float.intBitsToFloat((data[offset + 25] & 0xff) << 24 | (data[offset + 24] & 0xff) << 16 | (data[offset + 23] & 0xff) << 8 | (data[offset + 22] & 0xff));
                float score2 = Float.intBitsToFloat((data[offset + 29] & 0xff) << 24 | (data[offset + 28] & 0xff) << 16 | (data[offset + 27] & 0xff) << 8 | (data[offset + 26] & 0xff));
                float score3 = Float.intBitsToFloat((data[offset + 33] & 0xff) << 24 | (data[offset + 32] & 0xff) << 16 | (data[offset + 31] & 0xff) << 8 | (data[offset + 30] & 0xff));
                Student student = new Student(id, name, score1, score2, score3);
                students[i] = student;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return students;
    }

    private static Student findMaxAverage(Student[] students) {
        float maxAverage = 0;
        Student maxStudent = null;
        for (Student student : students) {
            float average = student.getTotal() / 3;
            if (average > maxAverage) {
                maxAverage = average;
                maxStudent = student;
            }
        }
        return maxStudent;
    }
}

这段代码中，我们使用了DataOutputStream来进行二进制数据的写入，并使用Files.readAllBytes和Byte数组的位运算来进行二进制数据的读取，其中22表示每个学生信息的长度。最后，我们使用findMaxAverage函数来寻找平均分最高的学生，并输出其所有信息。