public static String getSampleJsonString(int numRows) {
JSONStringer x = new JSONStringer();
Random rand = new Random(0);
try {
JSONWriter top = x.array();
for (int i = 1; i <= numRows; i++) {
JSONWriter o = top.object();
o.key("a").value("a" + i);
o.key("b").value("b" + i);