int writeJavaAnnotations(List<Attribute.Compound> attrs) {
        if (attrs.isEmpty()) return 0;
        ListBuffer<Attribute.Compound> visibles = new ListBuffer<Attribute.Compound>();
        ListBuffer<Attribute.Compound> invisibles = new ListBuffer<Attribute.Compound>();
        for (Attribute.Compound a : attrs) {
            switch (getRetention(a.type.tsym)) {
            case SOURCE: break;
            case CLASS: invisibles.append(a); break;
            case RUNTIME: visibles.append(a); break;
            default: ;// /* fail soft */ throw new AssertionError(vis);
            }
        }

        int attrCount = 0;
        if (visibles.length() != 0) {
            int attrIndex = writeAttr(names.RuntimeVisibleAnnotations);
            databuf.appendChar(visibles.length());
            for (Attribute.Compound a : visibles)
                writeCompoundAttribute(a);
            endAttr(attrIndex);
            attrCount++;
        }
        if (invisibles.length() != 0) {
            int attrIndex = writeAttr(names.RuntimeInvisibleAnnotations);
            databuf.appendChar(invisibles.length());
            for (Attribute.Compound a : invisibles)
                writeCompoundAttribute(a);
            endAttr(attrIndex);
            attrCount++;
        }
        return attrCount;
    }