如何通过引用复制和反序列化 java 中的对象列表？

Question

所以我是 Java 的初学者，我的教授让我们做这个作业，我一直在四处寻找，但我似乎找不到适合我的代码类型的正确答案。我们必须创建一个 class 文件，然后创建一个 public class 文件来测试它。

import java.io.Serializable;

public class Person implements Serializable {

    String Fname = new String();

    String MI = new String();

    String Lname = new String();

    String  age = new String();
    String gpa = new String();
//      int age = 20;

//      double gpa = 0.0;

    String Major = new String();

    String answer;


 //***********************************************
// The methods declared will go below 
// The first method is for the first name

public String getFname() {
   return Fname;
}

public void setFname(String Fname) {
       this.Fname = Fname;
    }


// This method is for the Middle Initial

public String getMI() {
   return MI;
}

 public void setMI(String MI) {
       this.MI = MI;
    }

// This method is for the Last name

public String getLname() {
       return Lname;    
}

    public void setLname(String Lname) {
       this.Lname = Lname;
    }

 // This method is for the Age

public String getAge() {
   return age;
}

public void setAge(String age) {
       this.age = age;
    }

// This method is for the GPA  

public String getGpa() {
   return gpa;
}

 public void setGpa(String gpa) {
       this.gpa = gpa;
    }

// This method is for the Major

public String getMajor() {
    return Major;
}
 public void setMajor(String Major) {
            this.Major = Major;
    }
}

Person.java 代码是可序列化的，应该写入 fhm 文件，然后反序列化以便将文件内容打印到终端 (Unix)。下面是主要代码，它是将读取 class Person 代码的 TestPerson 代码。

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

public class TestPerson {

public static void main(String[] args) throws IOException, ClassNotFoundException { 


Person[] Peeps = new Person[3];
Peeps[0] = new Person();
Peeps[1] = new Person();
Peeps[2] = new Person();

Scanner scan = new Scanner(System.in);
String Answer = new String();
String age1 = new String();
String gpa1 = new String();

for (int i = 0; i < Peeps.length - 1; i++) {
//  for (int i = 0; i < 3; i++) {   

System.out.print("What is the First Name? ");
Answer = scan.nextLine();
Peeps[i].setFname(Answer);

System.out.print("What is MI? ");
Answer = scan.nextLine();
Peeps[i].setMI(Answer);

System.out.print(" What is Last Name? ");
Answer = scan.nextLine();
Peeps[i].setLname(Answer);

System.out.print(" What is the Age? ");
age1 = scan.nextLine();
int age = Integer.parseInt(age1);
//  age = scan.nextInt();
Peeps[i].setAge(age1);

System.out.print(" What is the GPA? ");
gpa1 = scan.nextLine();
double gpa = Double.parseDouble(gpa1);
Peeps[i].setGpa(gpa1);

System.out.print(" What is the Major? ");
Answer = scan.nextLine();
Peeps[i].setMajor(Answer);
}

for (int i = 0; i < 3; i++) {
System.out.print(Peeps[i]); 
}

try {
  FileOutputStream fileOut = new FileOutputStream("Peeps.fhm");
  ObjectOutputStream out = new ObjectOutputStream(fileOut);
  out.writeObject(Peeps);
  out.close();
  fileOut.close();
  System.out.println("\nSerialization Successful\n");

} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

try { 
  FileInputStream fileIn = new FileInputStream("Peeps.fhm");
  ObjectInputStream in = new ObjectInputStream(fileIn);
  System.out.println("Deserialized Data: \n" + in.readObject().toString());
  in.close();
  fileIn.close();
} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}
}
}

我的教授要我提示用户在终端输入两个 Person 对象的数据，然后将对两个已填充 Person 之一的引用复制到最后一个 Person。然后程序会将所有三个人写入一个扩展名为“.fhm”的磁盘文件（我已经完成）。我的问题是如何复制参考文献？我的第二个问题也是如何正确反序列化文件，因为当我运行它时，它可以工作，但弹出的问题是它告诉我：

Deserialized Data: 
[LPerson;@5e481248

他想让它打印用户输入的信息。我检查了它写入的 fhm 文件，它收集了所有信息，所以我不确定我做错了什么。伙计们，我们将不胜感激，抱歉 post 有点长。提前致谢。

Answer 1

您的对象基本上是一个 Java 数组。要打印出来，您可以使用：

System.out.println("Deserialized Data: \n" + Arrays.toString(in.readObject()));

Answer 2

我不确定 "copy the reference" 部分是什么意思。

反序列化似乎运行良好。但是在您的代码中，您实际上只是调用 .toString() 来打印一个数组，这可能不是您想要的。您可能想要遍历项目并一一打印它们：

  FileInputStream fileIn = new FileInputStream("Peeps.fhm");
  ObjectInputStream in = new ObjectInputStream(fileIn);
  Person[] peeps = in.readObject();
  System.out.println("Deserialized Data:");
  for (Person person : peeps) { 
      System.out.printf("First Name: %s MI: %s Last Name: %s%n", 
          person.getFname(), person.getMI(), person.getLname()); 
  }

如何通过引用复制和反序列化 java 中的对象列表？

How to copy by reference and deserialize a list of objects in java?

java

arrays

serialization

reference

deserialization