Java Object reference -

this regarding usage of arraylist returned class instance variable.

class {      //assigned list of string it.     private list < string > newal;     //returns list     public list < string > getlist() {         return newa1;     } }  class test {      public void go() {         list < string > list = a.getlist();         list.add("");     }  } 

in test class when retreive list , manipulate list.because of reference ,class list got manipulated.if part of third party code.how correct code in test class original object wouldnt affected?

the arraylist constructor takes collection can use that:

list<string> list = new arraylist(a.getlist()); 

i think it's better this, depending on you're doing, may want construct new list in getter. helps type hiding.