class PdfNumberTree {

    private static final int leafSize = 64;

    /**
     * Creates a number tree.
     *
     * @param items  the item of the number tree. The key is an <CODE>Integer</CODE> and the value is a
     *               <CODE>PdfObject</CODE>.
     * @param writer the writer
     * @return the dictionary with the number tree.
     * @throws IOException on error
     */
    public static PdfDictionary writeTree(Map<Integer, ? extends PdfObject> items, PdfWriter writer)
            throws IOException {<FILL_FUNCTION_BODY>}

    private static void iterateItems(PdfDictionary dic, Map<Integer, PdfObject> items) {
        PdfArray nn = (PdfArray) PdfReader.getPdfObjectRelease(dic.get(PdfName.NUMS));
        if (nn != null) {
            for (int k = 0; k < nn.size(); ++k) {
                PdfNumber s = (PdfNumber) PdfReader.getPdfObjectRelease(nn.getPdfObject(k++));
                items.put(s.intValue(), nn.getPdfObject(k));
            }
        } else if ((nn = (PdfArray) PdfReader.getPdfObjectRelease(dic.get(PdfName.KIDS))) != null) {
            for (int k = 0; k < nn.size(); ++k) {
                PdfDictionary kid = (PdfDictionary) PdfReader.getPdfObjectRelease(nn.getPdfObject(k));
                iterateItems(kid, items);
            }
        }
    }

    public static HashMap<Integer, PdfObject> readTree(PdfDictionary dic) {
        HashMap<Integer, PdfObject> items = new HashMap<>();
        if (dic != null) {
            iterateItems(dic, items);
        }
        return items;
    }
}

        if (items.isEmpty()) {
            return null;
        }
        Integer[] numbers = new Integer[items.size()];
        numbers = items.keySet().toArray(numbers);
        Arrays.sort(numbers);
        if (numbers.length <= leafSize) {
            PdfDictionary dic = new PdfDictionary();
            PdfArray ar = new PdfArray();
            for (Integer number : numbers) {
                ar.add(new PdfNumber(number));
                ar.add(items.get(number));
            }
            dic.put(PdfName.NUMS, ar);
            return dic;
        }
        int skip = leafSize;
        PdfIndirectReference[] kids = new PdfIndirectReference[(numbers.length + leafSize - 1) / leafSize];
        for (int k = 0; k < kids.length; ++k) {
            int offset = k * leafSize;
            int end = Math.min(offset + leafSize, numbers.length);
            PdfDictionary dic = new PdfDictionary();
            PdfArray arr = new PdfArray();
            arr.add(new PdfNumber(numbers[offset]));
            arr.add(new PdfNumber(numbers[end - 1]));
            dic.put(PdfName.LIMITS, arr);
            arr = new PdfArray();
            for (; offset < end; ++offset) {
                arr.add(new PdfNumber(numbers[offset]));
                arr.add(items.get(numbers[offset]));
            }
            dic.put(PdfName.NUMS, arr);
            kids[k] = writer.addToBody(dic).getIndirectReference();
        }
        int top = kids.length;
        while (true) {
            if (top <= leafSize) {
                PdfArray arr = new PdfArray();
                for (int k = 0; k < top; ++k) {
                    arr.add(kids[k]);
                }
                PdfDictionary dic = new PdfDictionary();
                dic.put(PdfName.KIDS, arr);
                return dic;
            }
            skip *= leafSize;
            int tt = (numbers.length + skip - 1) / skip;
            for (int k = 0; k < tt; ++k) {
                int offset = k * leafSize;
                int end = Math.min(offset + leafSize, top);
                PdfDictionary dic = new PdfDictionary();
                PdfArray arr = new PdfArray();
                arr.add(new PdfNumber(numbers[k * skip]));
                arr.add(new PdfNumber(numbers[Math.min((k + 1) * skip, numbers.length) - 1]));
                dic.put(PdfName.LIMITS, arr);
                arr = new PdfArray();
                for (; offset < end; ++offset) {
                    arr.add(kids[offset]);
                }
                dic.put(PdfName.KIDS, arr);
                kids[k] = writer.addToBody(dic).getIndirectReference();
            }
            top = tt;
        }
    
<no_super_class>