Sorting a List alphabetically using compareTo() method

Question

I am writing a phonebook program in java and i need to list people in the list alphabetically and to do that i need to write a sorting algorithm for a list in java and it should use only compareTo() method. So can anyone help me to do that?

public void listAlpha()
 {
     Node tempNode = head;

     for(int i = 0; i <= size; i++)
        {
            for(int j = 0; j <= i; j++)
            {
                int comparison = ((tempNode.getNext().getElement().getName()).compareTo(tempNode.getElement().getName()));
                if(comparison < 0)
                {
                    Person tempPerson =  tempNode.getElement();

                    tempNode.setElement(tempNode.getNext().getElement());
                    tempNode.getNext().setElement(tempPerson);
                    tempNode = tempNode.getNext();
                }
            }


        }

(By the way this is a homework and i am using my own data structures.)

This is the class that method i wrote above belongs:

import java.util.*;

/** Singly linked list implementation .*/
public class SLinkedList<E> implements LinkedList<E>, Iterable<E> {
  protected Node<E> head;       // head node of the list
  protected Node<E> tail;       // tail node of the list
  protected int size;       // number of nodes in the list

    public Iterator<E> iterator()
    {
        return new LinkedListIterator(head);
    }

  /** Default constructor that creates an empty list */
  public SLinkedList() {
    head = null;
    tail = null;
    size = 0;
  }

  public int size() { 
    return size;
  }

  public boolean isEmpty() {
    return size == 0;
  }

  public void addFirst(E newElement) {
    Node<E> newNode = new Node(newElement,null);
    if(size == 0) //if list is empty
        tail = newNode;

    newNode.setNext(head);
    head = newNode;
    size++;
  }

  public void addLast(E newElement) {
    Node<E> newNode = new Node(newElement,null);

    if(size == 0) //if list is empty
        head = newNode;

    if (size != 0) //if list is not empty
        tail.setNext(newNode);

    tail = newNode;
    size++;
  }

  public E removeFirst() {
    Node<E> tempNode = null;
    if (size != 0) {
        if(size == 1)
            tail = null;

        tempNode = head;
        head = head.getNext();
        tempNode.setNext(null);
        size--;
    }

    //if list is empty then return null
    return tempNode.getElement(); 

  }

  public E removeLast() {
    Node<E> tempNode = head;

    if(size == 0)
        return null;

    if(size == 1) {
        head = null;
        tail = null;
        size--;
        return tempNode.getElement();
    }

    //size is greater than 1
    for(int i=1; i<=size-2; i++) {
        tempNode = tempNode.getNext(); //go to element that before the tail
    }

    Node<E> tempNode2 = tail;
    tail = tempNode;
    tail.setNext(null);
    size--;
    return tempNode2.getElement();

  }

  public void remove(E element){
    int index = 0;
    boolean found = false;
    Node<E> temp = head;
    for(int i=1; i<=size; i++) {//find the node with element
        index++;
        if(temp.getElement().equals(element)){
            found = true;
            break;
        }
        temp = temp.getNext(); 
    }

    if(found){
        if(index == 1) 
            removeFirst();

        else if(index == size)
            removeLast();

        else{   
            //find the previous node
            Node<E> prev = head;
            for(int i=1; i<index-1; i++) {
                prev = prev.getNext(); 
            }

            prev.setNext(temp.getNext());
            temp.setNext(null);
            size--;
        }
    }
  }

  public int searchList(E searchKey) {
    if(size == 0)
        return -1;

    Node tempNode = head;
    for(int i=1; i<=size; i++) {
        if(tempNode.getElement().equals(searchKey))
            return i; //return index of the node
        tempNode = tempNode.getNext();
    }

    return -1; //not found
  }

  public void printList() {
    Node tempNode = head;
    for(int i=1; i<=size; i++) {
        System.out.print(tempNode.getElement());
        if(i!=size) //if it is not last element
            System.out.print(" - ");
        tempNode = tempNode.getNext();
    }
    System.out.println();

  }

Person class:

public class Person
{
    private String name;
    private String surname;
    private String address;
    private PhoneNumber phone1;
    private PhoneNumber phone2;
    private PhoneNumber phone3;

    public Person()
    {
        name = null;
        surname = null;
        address = null;
        phone1.setPhone(0);
        phone1.setType("");
        phone2.setPhone(0);
        phone2.setType("");
        phone3.setPhone(0);
        phone3.setType("");
    }

    public Person(String n, String s, String a,PhoneNumber p1, PhoneNumber p2, PhoneNumber p3)
    {
        name = n;
        surname = s;
        address = a;
        phone1 = p1;
        phone2 = p2;
        phone3 = p3;

    }

    public String getName()
    {
        return name;
    }

    public void setName(String n)
    {
        name = n;
    }
    public String getSur()
    {
        return surname;
    }

    public void setSur(String s)
    {
        surname = s;
    }

    public void insertPhone(PhoneNumber phone)
    {
        if(phone2 == null)
            phone2 = phone;
        else if(phone3 == null)
            phone3 = phone;
    }

    public PhoneNumber getPhone1()
    {
        return phone1;
    }

    public PhoneNumber getPhone2()
    {
        return phone2;
    }

    public PhoneNumber getPhone3()
    {
        return phone3;
    }

    public String getAdd()
    {
        return address;
    }

    public void setAdd(String a)
    {
        address = a;
    }

Answer 1

You can make your Person class implement Comparable, and define the following method:

    public class Person implements Comparable<Person> {

       // Your previous code

       public int compareTo(Person other) {
          if (other == null) {
             // throw exception for example
          }
          return this.name.toLowerCase().compareTo(other.name.toLowerCase());
       }
    }