Question

我正在创建一个使用RandomAccessFile将学生详细信息存储在文件中的应用程序，但我实现此目的的唯一方法是将商店学生a，b，c，d，e等添加到静态数组中使用getBytes方法编写它。该商店使用arrayList。我已经尝试了很多东西和很多方法，但我不知道如何不使用静态数组。

这是我的代码：

MainApp

import java.io.IOException;
import java.io.RandomAccessFile;
public class MainApp
{

    public static void main(String[] args) throws Exception 
    {
        new MainApp().start();

    }
    public void start()throws Exception 
    {
        StudentStore details = new StudentStore();
        Student a = new Student("Becky O'Brien", "DKIT26", "0876126944", "bexo@hotmail.com");
        Student b = new Student("Fabio Borini", "DKIT28", "0876136944", "fabioborini@gmail.com");
        Student c = new Student("Gaston Ramirez", "DKIT29", "0419834501", "gramirez@webmail.com");
        Student d = new Student("Luis Suarez", "DKIT7", "0868989878", "luissuarez@yahoo.com");
        Student e = new Student("Andy Carroll", "DKIT9", "0853456788", "carroll123@hotmail.com");
        details.add(a);
        details.add(b);
        details.add(c);
        details.add(d);
        details.add(e);
        //details.print();


        RandomAccessFile file = new RandomAccessFile("ContactDetails.txt","rw");
        //getBytes() returns an array of bytes.
        //Because i have put the store in a static Array.(I done this because i could find no other
        //Simple way to write a Student Object.)
        //None of the methods of the RandomAccessFile write class worked with this.
        Student[] students = {a,b,c,d,e};
        details.write(students, file);
        details.readAll(file);



        file.close();


     }


 }

StudentStore

//---------------------------------------------------------------------------
//Imports.
//---------------------------------------------------------------------------   
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.List;
//---------------------------------------------------------------------------   

public class StudentStore
{
//---------------------------------------------------------------------------
//ArrayList declaration.
//---------------------------------------------------------------------------
    List<Student> students = new ArrayList<Student>();
//---------------------------------------------------------------------------
//Name:          Add method.
//Description:   Adds a student to the ArrayList.
//---------------------------------------------------------------------------
    public void add(Student student) 
    {
        students.add(student);
    }
//---------------------------------------------------------------------------
//Name:          DeleteAll method.
//Description:   Delete's everything in the ArrayList.
    //---------------------------------------------------------------------------
     public void deleteAll()
     {
           students.clear();
     }
//---------------------------------------------------------------------------
//Name:          Print method.
//Description:   Prints out the contents of the ArrayList.
//---------------------------------------------------------------------------
    public void print() 
    {
        for (int i = 0; i < students.size(); i++) 
        {
          Student a = students.get(i);
            System.out.println(a.toString());
        }
    }
    public int size()
    {
        return (students == null) ? 0 : students.size();
    }
    public void write(Student[] students, RandomAccessFile file) throws IOException
    {
        for (int i = 0; i < students.length; i++)
        {
        byte[] bytes = students[i].toString().getBytes();
        for(byte byteWrite : bytes)
        {
            file.writeByte(byteWrite);
        }
        }

    }
    public void readAll(RandomAccessFile file) throws IOException
    {
        final int Record_Length = 30;
        int recordNumber = 0;
        file.seek((recordNumber) * Record_Length);

        String code ="";
        for(int i = 0; i < 30; i++)
        {
        code += file.readLine() + "\n";
        }
        System.out.println(code);
    }

}

注意：我没有展示学生班，因为它是由构造函数，getter和setter以及toString组成的，我没有感觉使用上传它，但如果需要，我很乐意这样做。

Answer 1

您可以将Student标记为实施Serializable，因为它看起来只是存储了一堆文本。然后你可以从你的List<Student> students中获取字节来存储，如下所示：

ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(bos);
out.writeObject(students);
out.close();

byte[] bytes = bos.toByteArray();

然后你可以通过将文件中的字节读入字节数组然后执行以下操作将其从文件中提取出来：

ObjectInputStream in = new ObjectInputStream(new ByteArrayInputStream(bytes));
students = (List<Student>) in.readObject();
in.close();

编辑：只需将Student.toSting()写为您可以执行的字节：

public void write(RandomAccessFile file) throws IOException
{
    for (Student s: students)
    {
        byte[] bytes = s.toString().getBytes();
        for(byte byteWrite : bytes)
        {
            file.writeByte(byteWrite);
        }
    }

}

使用RandomAccessFile编写学生而不使用静态数组的另一种方法

1 个答案: