[Java] Read recorded in the Java Object – Read Write Object in Java

October 4, 2014 nguyenvanquan7826 EN Java 27 responses

To read recorded in the Java Object in the Object class in which we need to communicate java.io.Serializable

A simple example of reading record 1 Object MyStudent as follows:

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package VietSource.net.File;    // cac ban nho thay package cho phu hop
 
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
 
public class ReadWriteObject {
    public static void main(String[] args){
        MyStudent myStudent = new MyStudent(); // tao doi tuong myStudent
 
        //Ghi Object vao file
 
        try {   // dat try cacth de tranh ngoai le khi tao va viet File
            FileOutputStream f = new FileOutputStream("student.dat"); // tao file f tro den student.dat
            ObjectOutputStream oStream = new ObjectOutputStream(f); // dung de ghi theo Object vao file f
            oStream.writeObject(myStudent); // ghi MyStudent theo kieu Object vao file
            oStream.close();
        } catch (IOException e) {
            System.out.println("Error Write file");
        }
 
        // doc Object tu file
        MyStudent ms = null;
 
        try {   // dat try cacth de tranh ngoai le khi tao va doc File
            FileInputStream f = new FileInputStream("student.dat"); // tao file f tro den student.dat
            ObjectInputStream inStream = new ObjectInputStream(f);  // dung de doc theo Object vao file f
            // dung inStream doc theo Object, ep kieu tra ve la MyStudent
            ms = (MyStudent) inStream.readObject();
            inStream.close();
        } catch (ClassNotFoundException e) {
            System.out.println("Class not found");
        } catch (IOException e) {
            System.out.println("Error Read file");
        }
 
        // Xuat KQ
        System.out.println("My name is " + ms.name + ". I am " + ms.age + " years old");
    }
}
 
class MyStudent implements Serializable{
    String name = "Nguyen Van Quan";
    int age = 21;
}

Result: My name is Nguyen Van Quan. I am 21 years old
Noted: When you open the file student.dat you will find out this kind of data:

A more specific example of how to read and write, in this example 1 Student class attribute contains the name and age and the get method, set the value of their. A ProcessStudent class includes methods allow the student to enter from the keyboard, recorded on the student file, read from files by type Object and finally display the information read. In the code was explained quite clearly:

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package VietSource.net.File;
 
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Scanner;
 
public class IOFileObject_Student {
    public static void main(String args[]) throws Exception {
        ProcessStudent ps = new ProcessStudent();   // tao doi tuong cua lop ProcessStudent
        Student[] student1 = null, student2 = null; // tao 2 doi tuong student
        student1 = ps.creat();  // nhap student
        ps.write(student1);     // viet vao file
        student2 = ps.read();   // doc tu file
        ps.show(student2);      //hien thi kq
    }
}
 
class Student implements Serializable {     // Serializable dung de ghi va doc theo Object
    private static final long serialVersionUID = 1L;    // ID of Serializable
    private String name;
    private int age;
 
    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
 
    // cac ham get, set gia tri cac bien
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public int getAge() {
        return age;
    }
 
    public void setAge(int age) {
        this.age = age;
    }
 
}
 
// class xu ly thong tin
 
class ProcessStudent {
 
    public Student[] creat() {      // Input the data from Keyboard
        int n;
        Scanner scan = new Scanner(System.in);
 
        System.out.print("Enter number of student: ");
        n = Integer.parseInt(scan.nextLine());  //nhap so sinh vien
 
        Student[] student = new Student[n];
 
        for (int i = 0; i < n; i++) {
            System.out.print("Enter name: ");   // nhap ten sv thu i
            String name = scan.nextLine();
            System.out.print("Enter age: ");    // nhap tuoi
            int age = Integer.parseInt(scan.nextLine());    // tranh troi lenh nhu khi dung scan.nextInt()
            student[i] = new Student(name, age);    // khoi tao doi tuong Student thu i
        }
 
        scan.close();
        return student;
    }
 
    public void write(Student[] student) {  //ghi theo Object
        try {   // dat try cacth de tranh ngoai le khi tao va ghi File
            FileOutputStream f = new FileOutputStream("student.dat");   // tao file f tro den student.dat
            ObjectOutputStream oStream = new ObjectOutputStream(f); // dung de ghi theo Object vao file f
            oStream.writeObject(student);   // ghi student theo kieu Object vao file
            oStream.close();
        } catch (IOException e) {
            System.out.println("Error Write file");
        }
    }
 
    public Student[] read() {       // doc theo Object
        Student[] student = null;
        try {   // dat try cacth de tranh ngoai le khi tao va doc File
            FileInputStream f = new FileInputStream("student.dat"); // tao file f tro den student.dat
            ObjectInputStream inStream = new ObjectInputStream(f);  // dung de doc theo Object vao file f
            // dung inStream doc theo Object, ep kieu tra ve la Student
            student = (Student[]) inStream.readObject();
            inStream.close();
        } catch (ClassNotFoundException e) {
            System.out.println("Class not found");
        } catch (IOException e) {
            System.out.println("Error Read file");
        }
        return student;
    }
 
    public void show(Student[] student) throws Exception {      //In data doc duoc tu file ra man hinh
        try {
            for (int i = 0; i < student.length; i++) {
                System.out.println((i + 1) + " : My name is "
                        + student[i].getName() + ". I am "
                        + student[i].getAge() + " years old");
            }
        } catch (NullPointerException e) {
            System.out.println("File Empty");
        }
    }
}

Read more: Remember to add the object to the file in java