LimitedDocument.java

import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;

public class LimitedDocument extends PlainDocument {

    private int _maxLength  = -1;

    private String _allowCharAsString = null;


    public LimitedDocument(){
        super();
    }

    public LimitedDocument( int maxLength ){
        super();
        this._maxLength = maxLength;
    }

    public void insertString( int offset, String str, AttributeSet attrSet)
    throws BadLocationException{

        if(str == null) {
            return;
        }

        if(_allowCharAsString != null && str.length() == 1) {
            if(_allowCharAsString.indexOf(str) == -1){
                return;
            }
        }

        char[] charVal = str.toCharArray();
        String strOldValue = getText(0, getLength());
        byte[] tmp = strOldValue.getBytes();

        if(_maxLength != -1 && (tmp.length + charVal.length > _maxLength)){
            return;
        }

        super.insertString(offset, str, attrSet);
    }

    public void setAllowChar(String str) {
        _allowCharAsString = str;
    }
}