java - Problem of Logic in Addressbook, should have no blank entries or same entry... Please Help -

hope can me coding.

what need do: 1.) should not allow user have blank entry.. should prompt them "no name inputted!" 2.) should not allow user input same entry..

i have no idea how code i, please help.

here's complete code:

public class addressbook {

private addressbookentry entry[]; private int counter; private string sname; private int notfound=0;  public static void main(string[] args) {     addressbook = new addressbook();     a.entry = new addressbookentry[100];     int option = 0;     while (option != 5) {         string content = "choose option\n\n"                 + "[1] add entry\n"                 + "[2] delete entry\n"                 + "[3] update entry\n"                 + "[4] view entries\n"                 + "[5] view specific entry\n"                 + "[6] exit";         option = integer.parseint(joptionpane.showinputdialog(content));         switch (option) {             case 1:                 a.addentry();                 break;             case 2:                 a.deleteentry();                 break;             case 3:                 a.editentry();                 break;             case 4:                 a.viewall();                 break;             case 5:                 a.searchentry();                 break;             case 6:                 system.exit(1);                 break;             default:                 joptionpane.showmessagedialog(null, "invalid choice!");         }     } }  public void addentry() {     entry[counter] = new addressbookentry();     entry[counter].setname(joptionpane.showinputdialog("enter name: "));     entry[counter].setadd(joptionpane.showinputdialog("enter add: "));     entry[counter].setphoneno(joptionpane.showinputdialog("enter phone no.: "));     entry[counter].setemail(joptionpane.showinputdialog("enter e-mail: "));     counter++; }  public void viewall() {     string addtext = "  name\taddress\tphone no.\te-mail add\n\n";     int nonnull = 0;     (int = 0; < entry.length; i++) {         if (entry[i] != null) {             addtext = addtext + entry[i].getinfo() + "\n";             nonnull++;         }         if (nonnull == counter) {             break;         }     }     joptionpane.showmessagedialog(null, new jtextarea(addtext)); }  public void searchentry() {     sname = joptionpane.showinputdialog("enter name find: ");     searchmethod(); }  public void searchmethod() {     (int = 0; < counter; i++) {         if (entry[i].getname().equals(sname)) {             joptionpane.showmessagedialog(null, entry[i].getinfo2());             notfound = 0;             break;         } else {             notfound++;         }     }     if (notfound != 0) {         joptionpane.showmessagedialog(null, "name not found!");     } } public void editentry() {     int notfound = 0;     sname = joptionpane.showinputdialog("enter name edit: ");     (int = 0; < counter; i++) {         if (entry[i].getname().equals(sname)) {             entry[i] = new addressbookentry();             entry[i].setname(joptionpane.showinputdialog("enter new name: "));             entry[i].setadd(joptionpane.showinputdialog("enter new add: "));             entry[i].setphoneno(joptionpane.showinputdialog("enter new phone no.: "));             entry[i].setemail(joptionpane.showinputdialog("enter new e-mail: "));             notfound = 0;             break;         } else {             notfound++;         }     }     if (notfound != 0) {         joptionpane.showmessagedialog(null, "name not found!");     } } public void deleteentry() {     sname = joptionpane.showinputdialog("enter name delete: ");     (int = 0; < counter; i++) {         if (entry[i].getname().equals(sname)) {             joptionpane.showmessagedialog(null, "found!");             entry[i] = null;             break;         }     } } 

}

what happen code allows user click "ok" doesn't enter character yet.. , allows identical entry...

hope can me... need , yet still have no idea add in code... please lot..

what happen code allows user click "ok" doesn't enter character yet.. , allows identical entry...

the showinputdialog method lets user input string wants, or nothing. if don't want this, can either use self-made dialog, patch joptionpane (using subclass or such), or show dialog again when not 1 of given strings, this:

string input = joptionpane.showinputdialog(content); try {    option = integer.parseint(input); } catch(numberformatexception ex) {    // user typed nothing, or not integer    // todo: show error message    // => go next iteration of while loop.    continue;  } // , our switch ...