@@ -0,0 +1,756 @@
+package com.alibaba.json.bvt.issue_3600;%0A%0Aimport com.alibaba.fastjson.JSON;%0Aimport com.alibaba.fastjson.serializer.SerializerFeature;%0Aimport junit.framework.TestCase;%0A%0Apublic class Issue3655 extends TestCase %7B%0A%0A    public void test1() %7B%0A        B b = new B(null);%0A        System.out.println(JSON.toJSONString(b, SerializerFeature.WriteNullStringAsEmpty));%0A    %7D%0A%0A    public static abstract class A %7B%0A        public abstract Object getData();%0A    %7D%0A%0A    public static class B extends A %7B%0A        private String data;%0A%0A        public B(String data) %7B%0A            this.data = data;%0A        %7D%0A%0A        public String getData() %7B%0A            return this.data;%0A        %7D%0A%0A        public void setData(String data) %7B%0A            this.data = data;%0A        %7D%0A    %7D%0A%7D%0A

add testcase for #3655