将包含有学生学号、姓名、性别、专业、联系方式等信息的若干学生对象保存到文件stud.dat中，要求保密联系方式(即不保存)，然后再读取文件中的学生信息并按学号的升序输出，用Java编程实现，并显示输出结果

好的，我会为您解答这个问题。

Java代码如下：

import java.io.*;
import java.util.*;

class Student implements Serializable, Comparable<Student>{
    private static final long serialVersionUID = 1L;
    private String id;
    private String name;
    private String gender;
    private String major;
    private transient String phone;

    public Student(String id, String name, String gender, String major, String phone) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.major = major;
        this.phone = phone;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getGender() {
        return gender;
    }

    public String getMajor() {
        return major;
    }

    public String getPhone() {
        return phone;
    }

    @Override
    public int compareTo(Student student) {
        return this.id.compareTo(student.getId());
    }

    @Override
    public String toString() {
        return id + " " + name + " " + gender + " " + major;
    }
}

public class Main {
    public static void main(String[] args) {
        ArrayList<Student> students = new ArrayList<>();
        students.add(new Student("10001", "张三", "男", "计算机科学与技术", "13512345678"));
        students.add(new Student("10002", "李四", "女", "软件工程", "13612345678"));
        students.add(new Student("10003", "王五", "男", "信息安全", "13712345678"));
        students.add(new Student("10004", "赵六", "女", "物联网工程", "13812345678"));

        try(ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("stud.dat"))) {
            for(Student s : students) {
                oos.writeObject(s);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        ArrayList<Student> studentsFromFile = new ArrayList<>();
        try(ObjectInputStream ois = new ObjectInputStream(new FileInputStream("stud.dat"))) {
            while(true) {
                studentsFromFile.add((Student)ois.readObject());
            }
        } catch (EOFException e) {
            // 文件读取结束
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }

        Collections.sort(studentsFromFile);

        for(Student s : studentsFromFile) {
            System.out.println(s.toString());
        }
    }
}

该程序定义了一个`Student`类，包含学号、姓名、性别、专业和联系方式等信息，其中联系方式被标记成`transient`，表示不会被序列化到文件中。程序先将4个`Student`对象保存到文件`stud.dat`中，然后再从该文件中读取学生信息，并按学号的升序输出。