how to define value object for file in java

Question

I wrote a program that creates 3 files with .txt format and writes some data's into them. Now I am asked to define a value object for these files, And override the toString method, And then when I read the files Set them in to Value objects. Now I'm completely confused and do not know where to start. Thank you in advance for your help

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@Dren Of course not! The problem is that I do not know where to start, Although I searched a lot — Pourya Siyami, Mar 09 '21 at 13:56
@PouryaSiyami if you tell us what is the content of the file we can help you then. — Dren, Mar 09 '21 at 13:57
@PouryaSiyami Based on your question although without seeing what the context of the file is it is difficult to give a correct answer, but I assumed a case where you will create objects from the file, so see if you have any questions you can ask me. — Dren, Mar 09 '21 at 14:27
@Dren Thanks for taking the time to respond, Yes, your answer was very close to what I wanted. — Pourya Siyami, Mar 09 '21 at 14:47

Dren · Accepted Answer · 2021-03-09T14:49:07.887

If you want to create objects from text files first what are you going to do is read the file. There are many available classes in the Java API that can be used to read files: BufferedReader, FileReader etc. The number of objects you will create will depend on the number of lines in the file. For example if you have a file with the following content

PersonName1,PersonSurname1,20
PersonName2,PersonSurname2,22
PersonName3,PersonSurname3,23

Let's say that these lines represent name, surname, and age of some users

What you need to do first is create a class that will represent this object, as we see in the text file the object will contain three parameters , so you create a class with three atribbutes

public class Person {

    private String name;
    private String surname;
    private Integer age;

    public Person(String name, String surname, Integer age) {
        this.name = name;
        this.surname = surname;
        this.age = age;
    }

    @Override
    public String toString() {
        return "NAME : " + name + " : " + surname;
    }

Now comes the reading part , for reading the file we will use BufferedReader, we read every line of the file by splitting the line by commas(,) for every iteration

String [] parameters = line.split(",");

This array of String now will represent our user attributes so we access it

        String name = parameters[0];
        String surname = parameters[1];
        Integer age = Integer.parseInt(parameters[2]);

And now we create an object of Person every iteration and we add it to the list

      Person p = new Person(name,surname,age);
      list.add(p);

Example

BufferedReader bufferedReader = new BufferedReader(new FileReader("test.txt"));

        List<Person> list = new ArrayList<>();

        String line = null;

    

while((line = bufferedReader.readLine())!=null){
        try {
            String[] parameters = line.split(",");
            if(parameters.length == 3) {
                String name = parameters[0];
                String surname = parameters[1];
                Integer age = Integer.parseInt(parameters[2]);
                Person p = new Person(name, surname, age);
                list.add(p);
            }
        }catch (NumberFormatException e){
        }
    }

    System.out.println("Object created from the file");
    list.stream().forEach(System.out::println);

OUTPUT

NAME : PersonName1 : PersonSurname1
NAME : PersonName2 : PersonSurname2
NAME : PersonName3 : PersonSurname3

how to define value object for file in java

1 Answers1