Question

What Exception do I need to add to my try catch block if I want to detect if a user has entered any characters?

This is my code where I want to know if the user hasn’t input anything or if the user’s input was already saved in an addressbook. I am using an array to store my entries:

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++;
}

Do I need a try-catch or a condition? 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;
    try {
        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.searchEntry();
                    break;
                case 6:
                    System.exit(1);
                    break;
                default:
                    JOptionPane.showMessageDialog(null, "Invalid Choice!");
            }
        }
    }catch(NumberFormatException e){
        JOptionPane.showMessageDialog(null, "Please Choose a Number in the displayed Menu");
    }
}

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() {
    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;
        }
    }
}

}

I am having problem with my addEntry() method, because I want to detect if the user’s new added entry was already stored in my addressbook and if the user doesn’t typed anything when I ask “Enter Name:” in JOptionPane and still press OK.

Answer 1

From your updated question, it appears as if you are talking about user input from dialog boxes. The javadoc says that the showInputDialog methods return either the user’s String (which could be empty) or null if the user canceled the dialog.

No exception is thrown. The user canceling the dialog is not “exceptional”.