New to OOP Java syntax

Question

Hello there, I'm new here and I'd be thankful if you help me a bit with my self introduction to Java. I'll write down a source of main and hope you will tell me my beginner's problems:
import java.util.*;
//public int createdInstances = 0;
public class Students{
     private String name;
     private String course;
     public Enum Specialty{
          administrator, developer, designer, none
     public Specialty specialty;
     public Enum University{
          TU, SU, NBU, none
     public University university;
     private String email;
     private long phone;
     public static int instances;
     public Students(){
          this.name = "nullStudent";
          this.course = "nullCourse";
          specialty = Specialty.none;
          university = University.none;
          this.email = "none";
          this.phone = 0;
     public Students(String name, String course)     {
          this.name = name;
          this.course = course;
          specialty = Specialty.none;
          university = University.none;
          this.email = "none";
          this.phone = 0;
     public Students(String name, String course, String email, long phone){
          this.name = name;
          this.course = course;
          this.email = email;
          this.phone = phone;
     public void Viewer(){
          System.out.println("Name: " + name + " course: " + course + " @email: " + email + " #phone: " + phone);
public class Tasks{
     public static void main(String args[]){
          Students guys = new Students();
          guys.Viewer();
}Thanks in advance.

Answer 1

You can make a method that converts a string to a Server like this:
    enum Server {
        CPU, RAM, HDD
    public Server stringToServer( String s ) {
        if ( s == "CPU" ) {
            return Server.CPU;
        } else if ( s == "RAM" ) {
            return Server.RAM;
        } else if ( s == "HDD" ) {
            return Server.HDD;
        } else {
            throw new IllegalArgumentException(); // or any other error handler :)
    }