How to convert Arraylist to Json in Java -

i have arraylist, arraylist holds bunch of domain object. it's below showed:

domain [domainid=19, name=a, dnsname=a.com, type=0, flags=0] domain [domainid=20, name=b, dnsname=b.com, type=0, flags=12] domain [domainid=21, name=c, dnsname=c.com, type=0, flags=0] domain [domainid=22, name=d, dnsname=d.com, type=0, flags=0] 

my question how convert arraylist json? data format should be:

{   "param":{     "domain":[       {         "domid":19,       "name":"a",       "dnsname":"a.com",       "type":0,       "flags":     },     ...   ] } 

not sure if it's need, can use gson library (link) arraylist json conversion.

arraylist<string> list = new arraylist<string>(); list.add("str1"); list.add("str2"); list.add("str3"); string json = new gson().tojson(list); 

or in case:

arraylist<domain> list = new arraylist<domain>(); list.add(new domain()); list.add(new domain()); list.add(new domain()); string json = new gson().tojson(list); 

if reason find more convenient, can iterate through arraylist , build json individual domain objects in list

string tojson(arraylist<domain> list) {     gson gson = new gson();     stringbuilder sb = new stringbuilder();     for(domain d : list) {         sb.append(gson.tojson(d));     }     return sb.tostring(); }