java - combining two arraylist into a single linked list in one go -

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i getting list shown below

 list<string> tr = newdatamap.get("b1").getref();  list<string> tr2 = newdatamap.get("b1").getms();

now can see have 2 arraylists want store contents single list itself. that:

list<string> tr = newdatamap.get("b1").gettraderef() + newdatamap.get("b1").gettms();

but showing error. please advise how can combine them single linked list.

if want produce new list content of tr , tr2, can try with:

list<string> list = new arraylist<>(){{ addall(tr); addall(tr2); }};

if want append t2 tr, can do:

list<string> tr = newdatamap.get("b1").getref().addall(newdatamap.get("b1").getms());

Macro