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

hope you can help me coding.

What i need to do: 1.) I should not allow user to have a blank entry.. I should prompt them like "No name inputted!" 2.) I should not allow user to input same entry..

I have no Idea how to code i, please help.

Here's my 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 a = new AddressBook();
    a.entry = new AddressBookEntry[100];
    int option = 0;
    while (option != 5) {
        String content = "Choose an Option\n\n"
                + "[1] Add an Entry\n"
                + "[2] Delete an Entry\n"
                + "[3] Update an Entry\n"
                + "[4] View all 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.searchEn开发者_如何转开发try();
                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;
    for (int i = 0; i < 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 to find: ");
    searchMethod();
}

public void searchMethod() {
    for (int i = 0; i < 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 to edit: ");
    for (int i = 0; i < 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 to delete: ");
    for (int i = 0; i < counter; i++) {
        if (entry[i].getName().equals(SName)) {
            JOptionPane.showMessageDialog(null, "Found!");
            entry[i] = null;
            break;
        }
    }
}

}

What happen to my code was it allows user to click "OK" even he doesn't enter any character yet.. and it also allows identical entry...

Hope you can help me... i need it very soon and yet i still have no Idea what to add in my code... please help thanks a lot..

What happen to my code was it allows user to click "OK" even he doesn't enter any character yet.. and it also allows identical entry...

The showInputDialog method lets the user input any string he wants, or also nothing. If you don't want this, you can either use a self-made dialog, patch the JOptionPane (using a subclass or such), or simply show the dialog again when it is not one of your given strings, like this:

String input = JOptionPane.showInputDialog(content);
try {
   option = Integer.parseInt(input);
}
catch(NumberFormatException ex) {
   // the user typed nothing, or something that is not an integer
   // TODO: show error message
   // => go to next iteration of while loop.
   continue; 
}
// and now our switch ...