@@ -0,0 +1,665 @@
+package com.alibaba.json.bvt.bug;%0A%0Aimport java.util.HashMap;%0Aimport java.util.Map;%0A%0Aimport org.junit.Assert;%0A%0Aimport com.alibaba.fastjson.JSON;%0Aimport com.alibaba.fastjson.JSONObject;%0A%0Aimport junit.framework.TestCase;%0A%0Apublic class Bug_for_issue_320 extends TestCase %7B%0A%0A    @SuppressWarnings(%7B %22rawtypes%22, %22unchecked%22 %7D)%0A    public void test_for_issue() throws Exception %7B%0A        Map map = new HashMap();%0A        map.put(1001L, %22aaa%22);%0A        %0A        String text = JSON.toJSONString(map);%0A        Assert.assertEquals(%22%7B1001:%5C%22aaa%5C%22%7D%22, text);%0A        %0A        JSONObject obj = JSON.parseObject(text);%0A        Assert.assertEquals(%22aaa%22, obj.get(%221001%22));%0A    %7D%0A%0A%7D%0A

add testcase for issue 320. https://github.com/alibaba/fastjson/issues/320