I want to read all the objects I write to the file, but I can only read the first one at the beginning

I would like to serialize and de-serialize and read and write objects to the file.I can do additional writing, but I can't read it well.
No matter how many times you load it, you can only get the first object written to the file.

I want to load all objects that I wrote to the file.

I thought of turning the loop with the main function, and I used RandomAccessFile to move the file pointer, but it didn't work.
There was also a way to read one line at a time, but if the object has a different type, an error will occur.

If anyone knows how to do it well, please let me know.
Thank you for your cooperation.

Member.java File

package hello;

import java.io.Serializable;

public class member implements Serializable {

    public String name;// Name
    public age;// age
}

SerializableSampleTest.java File

package hello;
import java.io.FileInputStream;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;


public class SerializableSampleTest{
    public static void main(String[]args) {
        SerializableSampleTest1 = new SerializableSampleTest();
        SerializableSampleTest2 = new SerializableSampleTest();


        // first person
        Member mb1 = new Member();
        mb1.name="sakura";
        mb1.age = 20;

        List Akumi = new ArrayList();
        Akumi.add (mb1.name);
        Akumi.add(mb1.age);

        sst1.write(Akumi);

        // second person
        Member mb2 = new Member();
        mb2.name="yuri";
        mb2.age = 19;

        List Bkumi = new ArrayList();
        Bkumi.add (mb2.name);
        Bkumi.add(mb2.age);

        sst2.write(Bkumi);


        System.out.println(sst1.read());
        System.out.println(sst2.read());



    }

 public void write(java.util.List<Member>Mem){
     // serialization
     try(ObjectOutputStreamoos=newObjectOutputStream(newFileOutputStream("member", true))){
         oos.writeObject(Mem);
         System.out.println("Serialization Complete";
         oos.close();

     } catch(IOExceptione){
         System.out.println("error");
     }
 }

 public java.util.List<Member>read(){
     java.util.List<Member>Mem=null;

     // de-serialization
     try(ObjectInputStream ois=newObjectInputStream(newFileInputStream("member")){
         Mem=(List<Member>)ois.readObject();
         System.out.println("Decialization Complete";
         ois.close();
     } catch(IOException | ClassNotFoundException) {
         System.out.println("error");
     }
     return Mem;
  }

 }

java

2022-09-29 22:10

1 Answers

Is it like this?

public class SerializableSampleTest{
  try(ObjectOutputStreamoos=newObjectOutputStream(newFileOutputStream("member")){
    // first person
    Member mb1 = new Member();
    mb1.name="sakura";
    mb1.age = 20;
    oos.writeObject(mb1);

    // second person
    Member mb2 = new Member();
    mb2.name="yuri";
    mb2.age = 19;
    oos.writeObject(mb2);

    System.out.println("Serialization Complete";
  } catch(IOExceptione){
    System.out.println("error");
  }

  try(ObjectInputStream ois=newObjectInputStream(newFileInputStream("member")){
    while(true){
      Member mem=(Member)ois.readObject();
      System.out.println(mem);
    }
  } catch(EOFExceptione){
    System.out.println("Decialization Complete";
  } catch(IOException | ClassNotFoundException) {
    System.out.println("error");
  }
}

First of all, the List is used incorrectly.Please check again.
You do not need to use List.

Also, ObjectOutputStream is AutoCloseable, so you don't need to close() in that block if you use the try-with-resources statement.

Also, you do not need to open two ObjectOutputStream to writeObject().
The same goes for readObject().
It's better not to open it.

You can determine if readObject() has read all objects, because FileInputStream is wrapped, you can use EOFException.

2022-09-29 22:10

If you have any answers or tips

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