POI setting Cell Background to a Custom Color

Question

I want to set custom color to a cell\'s background.
I use HSSFWorkbook (can\'t use anything else).

HSSFPalette palette = aWorkBook.getCustom         


        

Answer 1

As pointed in Vlad's answer, you are running out of free color slots. One way to get around that would be to cache the colors: whenever you try a RGB combination, the routine should first check if the combination is in the cache; if it is in the cache, then it should use that one instead of creating a new one from scratch; new colors would then only be created if they're not yet in cache.

Here's the implementation I use; it uses XSSF plus Guava's LoadingCache and is geared towards generationg XSSF colors from CSS rgb(r, g, b) declarations, but it should be relatively trivial to adapt it to HSSF:

    private final LoadingCache colorsFromCSS = CacheBuilder.newBuilder()
            .build(new CacheLoader() {

                private final Pattern RGB = Pattern.compile("rgb\\(\\s*(\\d+)\\s*, \\s*(\\d+)\\s*,\\s*(\\d+)\\s*\\)");

                @Override
                public XSSFColor load(String style) throws Exception {
                    Matcher mat = RGB.matcher(style);
                    if (!mat.find()) {
                        throw new IllegalStateException("Couldn't read CSS color: " + style);
                    }                       
                    return new XSSFColor(new java.awt.Color(
                            Integer.parseInt(mat.group(1)), 
                            Integer.parseInt(mat.group(2)), 
                            Integer.parseInt(mat.group(3))));
                }

            });

Perhaps someone else could post a HSSF equivalent? ;)