java - Please Help Fix My add Method -

it supposed keep contact_list in alphabetical order last name. have been @ hours , cannot figure out. added post both add method , findcontactindex method supposed find index of contact. keep getting nullpointer exceptions , other errors. need find out goes alphabetically , insert new contact there , move ones come after down, in correct order.

 public void add(contact frnd)   {      if(numcontacts == 0)      {       contact_list[0] = frnd;      }      else      {          for(int = 0; < numcontacts; i++)          {           int x =contact_list[i].getlastname().comparetoignorecase(frnd.getlastname());           if(x < 0)           {              contact_list[findcontactindex(contact_list[i].getlastname())] = frnd;              break;           }       }   }   numcontacts++;   }      /**    * searches contact_list find contact last name    * @param lstnm last name of contact found    * @return indexofcontact index of contact has been found    */    public int findcontactindex(string lstnm)    {        int indexofcontact = -1; // defaults @ 0 incase name not found        for(int = 0; < numcontacts; i++) // once every contact        {           int = lstnm.compareto(contact_list[i].getlastname());           if( == 0) // if contact found           {                indexofcontact = i; // assign index of contact           }         }        return indexofcontact;         } 

here code use array. below main method tests code.

public class contactlist {  static class contact {     string lastname;      contact(final string lastname) {         this.lastname = lastname;     }      @override     public string tostring() {         return string.format("contact[%s]", this.lastname);     } }  static final int max_contacts = 10;  contact[] contactlist = new contact[max_contacts];  void add(final contact newcontact) {     if (newcontact == null || newcontact.lastname == null) {         return;     }     contact contacttoadd = newcontact;     (int pos = 0; pos < max_contacts; pos++) {          final contact current = this.contactlist[pos];         if (current == null) { // found end, we're done             this.contactlist[pos] = contacttoadd;             break;         } else if (current.lastname.compareto(contacttoadd.lastname) > 0) { // current comes after contacttoadd             this.contactlist[pos] = contacttoadd;             contacttoadd = current;         }     } }  static final string[] lastnames = { "a", "c", "e", "b", "d", null };  public static void main(final string[] args) {     final contactlist contactlist = new contactlist();     (final string lastname : lastnames) {         final contact contact = new contact(lastname);         contactlist.add(contact);         system.out.println(arrays.tostring(contactlist.contactlist));     } } 

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