package MainJava;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
public class FilterString extends DocumentFilter 
{    
    @Override    
    public void replace(FilterBypass fb, int i, int j, String str, AttributeSet as) throws BadLocationException 
    {        
        for (int n = str.length(); n > 0; n--) 
        {            
            char c = str.charAt(n - 1);
            if (Character.isLetter(c) || c == ' ') 
            {
            super.replace(fb, i, j, String.valueOf(c), as); 
            }
            else 
            {                
                java.awt.Toolkit.getDefaultToolkit().beep();
            }
        }
    }
}