Printing out all the objects in array list

Question

I need to be able to print out the Student objects(all variables) in my array list. Is this possible? When i try to print it outputs this sort of thing e.g student.Student@82701e. I think it's hexadecimal or something

This is my code:

package student;

public class Student {

    private String studentName;
    private String studentNo;
    private String email;
    private int year;


    public Student() {
        this.studentName = null;
        this.studentNo = null;
        this.email = null;
        this.year = -1;
    }

    public Student(String nName, String nNum, String nEmail, int nYr) {
        this.studentName = nName;
        this.studentNo = nNum;
        this.email = nEmail;
        this.year = nYr;
    }

    public void setStudentName(String newStudentName) {
        this.studentName = newStudentName;
    }

    public void setStudentNo(String newStudentNo) {
        this.studentNo = newStudentNo;
    }

    public void setEmail(String newEmail) {
        this.email = newEmail;
    }

    public void setYear(int newYear) {
        this.year = newYear;
    }

    public String getStudentName() {
        return studentName;
    }

    public String getStudentNo() {
        return studentNo;
    }

    public String getEmail() {
        return email;
    }

    public int getYear() {
        return year;
    }
}

package student;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class studentTest {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);



        List<Student> Students = new ArrayList();


        Student student1 = new Student();

        student1.setStudentName("Bob Marley");
        student1.setStudentNo("N0002");
        student1.setEmail("student2@student.com");
        student1.setYear(2);

        Students.add(student1);

        Student student2 = new Student();

        student2.setStudentName("Bill Harvey");
        student2.setStudentNo("N0003");
        student2.setEmail("student3@student.com");
        student2.setYear(2);

        Students.add(student2);

        Student student3 = new Student();

        student3.setStudentName("John Beans");
        student3.setStudentNo("N0004");
        student3.setEmail("student4@student.com");
        student3.setYear(2);

        Students.add(student3);


        System.out.println("Add new students: ");
        System.out.println("Enter number of students to add: ");
        int countStudents = input.nextInt();

        for (int i = 0; i < countStudents; i++) {
            Student newStudents = new Student();


            System.out.println("Enter details for student: " + (i + 1));

            System.out.println("Enter name: ");
            newStudents.setStudentName(input.next());

            System.out.println("Enter Number: ");
            newStudents.setStudentNo(input.next());System.out.println("Search by student number: ");



            System.out.println("Enter email: ");
            newStudents.setEmail(input.next());

            System.out.println("Enter year: ");
            newStudents.setYear(input.nextInt());
            Students.add(newStudents);
        }


    }
}

The [tag:homework] tag is depricated. – Travis J Oct 21 '12 at 19:37 — Travis J, Oct 21 '12 at 19:37

score 20 · Accepted Answer · answered Oct 21 '12 at 19:40

Override toString() method in Student class as below:

   @Override
   public String toString() {
        return ("StudentName:"+this.getStudentName()+
                    " Student No: "+ this.getStudentNo() +
                    " Email: "+ this.getEmail() +
                    " Year : " + this.getYear());
   }

Rohit Jain · Answer 2 · 2012-10-21T19:47:53.620

Whenever you print any instance of your class, the default toString implementation of Object class is called, which returns the representation that you are getting. It contains two parts: - Type and Hashcode

So, in student.Student@82701e that you get as output ->

student.Student is the Type, and
82701e is the HashCode

So, you need to override a toString method in your Student class to get required String representation: -

@Override
public String toString() {
    return "Student No: " + this.getStudentNo() + 
           ", Student Name: " + this.getStudentName();
}

So, when from your main class, you print your ArrayList, it will invoke the toString method for each instance, that you overrided rather than the one in Object class: -

List<Student> students = new ArrayList();

// You can directly print your ArrayList
System.out.println(students); 

// Or, iterate through it to print each instance
for(Student student: students) {
    System.out.println(student);  // Will invoke overrided `toString()` method
}

In both the above cases, the toString method overrided in Student class will be invoked and appropriate representation of each instance will be printed.

score 4 · Answer 3 · answered Oct 21 '12 at 19:35

4

You have to define public String toString() method in your Student class. For example:

public String toString() {
  return "Student: " + studentName + ", " + studentNo;
}

answered Oct 21 '12 at 19:35

Andrew Logvinov

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1

If you are using eclipse you can do it automatically with clicking Source -> generate toString() – amit Oct 21 '12 at 19:37
This might sound silly (sorry I'm still learning) but if I define that method how to I access the arraylist from it. – joe Oct 21 '12 at 19:37
1

@Rob When you use `System.out.println()` to print your list, for example, JVM will automatically invoke the `toString()` method on the objects that your list contains. In your case, these will be `Student`s. – Andrew Logvinov Oct 21 '12 at 19:41

Printing out all the objects in array list

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