Simple Linked List add and list implementation

Tree.java

package oasis;

public class Tree {
    public Student head = null;

    public void add(Integer number, String name, String surname) {
        Student student = new Student(number, name, surname);
        if (head == null) {
            head = student;
        } else {
            Student temp = head;
            while (temp.next != null) {
                temp = temp.next;
            }
            temp.next = student;
        }
    }

    @Override
    public String toString() {
        return "Tree [head=" + head + "]";
    }

    public void list() {
        Student temp = head;
        while (temp != null) {
            System.out.println(temp.toString());
            temp = temp.next;
        }
    }
}

class Student {
    public Integer number;
    public String  name;
    public String  surname;
    public Student next;

    public Student() {
        super();
    }

    public Student(Integer number, String name, String surname) {
        this.number = number;
        this.name = name;
        this.surname = surname;
    }

    @Override
    public String toString() {
        return "Student [number=" + number + ", name=" + name + ", surname=" + surname + ", next=" + next + "]";
    }

}