printable char in java

问题:

Does anyone knows how to detect printable characters in java?

After a while ( trial/error ) I get to this method:

    public boolean isPrintableChar( char c ) {
        Character.UnicodeBlock block = Character.UnicodeBlock.of( c );
        return (!Character.isISOControl(c)) &&
                c != KeyEvent.CHAR_UNDEFINED &&
                block != null &&
                block != Character.UnicodeBlock.SPECIALS;
    }

I'm getting the input via KeyListener and come Ctr-'key' printed an square. With this function seems fairly enough.

Am I missing some char here?

回答1:

It seems this was the "Font" independent way.

public boolean isPrintableChar( char c ) {
    Character.UnicodeBlock block = Character.UnicodeBlock.of( c );
    return (!Character.isISOControl(c)) &&
            c != KeyEvent.CHAR_UNDEFINED &&
            block != null &&
            block != Character.UnicodeBlock.SPECIALS;
}

回答2:

I'm not perfectly sure whether I understand your problem. But if you want detect if character can be drawn to Graphics object, and if not print some placeholder char you might find usefull:

Font.canDisplay(int)

It will check whether font can display specific codepoint (it is more that check whether font is displayable at all -- since there are chars that are displayable - like ą - but some fonts cant display them.