Phone number validation in java swing

Question

I'm creating a form in java swing and I need to verify that the user has indeed entered phone number and not "abcde".

Do I put the code in the Jbutton area or the text field area?

I'm looking to use a try/catch to throw an exception. My specific question is where does the code go?

You could use a `DocumentFilter` to restrict what the user can input and constrain the number of characters they can input. You can have a look at [Text Component Features](https://docs.oracle.com/javase/tutorial/uiswing/components/generaltext.html) for more details — MadProgrammer, Jan 27 '18 at 02:48
[`DocumentFilter` to limit the number of characters](https://stackoverflow.com/questions/15166921/how-to-set-documentfilter-with-input-length-and-range-e-g-1-3-or-10-80/15168429#15168429) — MadProgrammer, Jan 27 '18 at 02:50

score 1 · Answer 1 · answered Jan 27 '18 at 03:29

I would recommend using a DocumentFilter, which would allow you to perform a real time filter as the user types.

The following is a very basic example of filtering out unwanted characters and limit the length of how many characters can be entered

public class PhoneNumberDocumentFilter extends DocumentFilter {

    protected static String[] VALID_VALUES = new String[]{"+", "-", " ", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0"};

    private int maxLength = 21;

    public PhoneNumberDocumentFilter(int maxLength) {
        this.maxLength = maxLength;
    }

    public PhoneNumberDocumentFilter() {
    }

    protected String filter(String text) {
        StringBuilder sb = new StringBuilder();
        List<String> validValues = Arrays.asList(VALID_VALUES);
        for (int index = 0; index < text.length(); index++) {
            String value = text.substring(index, index + 1);
            if (validValues.contains(value)) {
                sb.append(value);
            }
        }
        return sb.toString();
    }

    @Override
    public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {

        Document doc = fb.getDocument();
        StringBuilder sb = new StringBuilder();

        sb.append(doc.getText(0, doc.getLength()));
        sb.insert(offset, string);
        String value = filter(string);
        if (value.length() > 0) {
            if (maxLength > 0 && doc.getLength() + value.length() <= maxLength) {
                super.insertString(fb, offset, value, attr);
            }
        }
    }

    @Override
    public void replace(FilterBypass fb, int offset, int length, String text,
                    AttributeSet attrs) throws BadLocationException {

        Document doc = fb.getDocument();
        StringBuilder sb = new StringBuilder(2);
        sb.append(doc.getText(0, doc.getLength()));
        sb.replace(offset, offset + length, text);

        String value = filter(text);
        if (value.length() > 0) {
            if (sb.length() > maxLength) {
                length = sb.length() - maxLength;
                if (length > 0) {
                    value = value.substring(0, length);
                }
            }
            super.replace(fb, offset, length, value, attrs);
        }

    }
}

What it doesn't do is valid the format, I'll leave that up to you to figure out how you might do that

score 1 · Accepted Answer · answered Jan 27 '18 at 03:35

Whether the code should be put for JButton or JTextField that is coder's choice. But in both ways you have to follow different ideas.

1. In JButton: If you put your code inside JButton, it is easiest. You may use simple try-catch. But it's main drawback is your phone number validation will occur after clicking on that JButton. But users can still provide wrong input and they are not notified unless they click on the JButton.

2. Using DocumentFilter: You may want to send notice to users in real time, when they are typing on the text field. In that case, you have to use DocumentFilter. Here is the official link of DocumentFilter from Oracle where the procedure is described clearly.

Phone number validation in java swing

2 Answers2