Is this a good isNaN method? public boolean isNaN(String string){

@SuppressWarnings("unused")
BigDecimal bg = null;

try{

    bg = new BigDecimal(string);

}catch(Exception e){

    return true;
}

return false;
}


There is no native isNaN method for BigDecimal.  The thing I don't like about this method is the suppressed warning. I never use the variable but only the constructor to see if it doesn't throw an exception.  If it does, I return the corresponding boolean.

What do you think?
You said : 


  I never use the variable but only the constructor to see if it doesn't throw an exception


I would ask you, then why did you declare a variable at all ? You could have done : 

public boolean isNaN(final String string) {
    try {
       new BigDecimal(string);
    } catch (final Exception e) {
        return true;
    }
    return false;
}


When you don't need a variable, don't declare it.

You should not catch Exception because it's too generic. What do you really want ? The constructor throw NumberFormatException if the argument is not valid, the better option would be to catch that one instead.