The difference between the RemoveAll (collection<e> Col) and the clear method of the list collection

RemoveAll () method
Privatestaticvoid  testlist () {        Listnew arraylist<string>() ;        ListNew arraylist<string>();        List.add ("123");        List.add ("456");        List1.add ("123");        List.removeall (list1);        Iterator<String> Iterator = list1.iterator ();          while (Iterator.hasnext ()) {            System.out.println (Iterator.next ());        }                    }

// Output Results 456

//clear () method
Private Static voidtestlist () {List<String> list =NewArraylist<string>(); List<String> List1 =NewArraylist<string>(); List.add ("123"); List1.add ("123"); List.add ("456");        List.clear (); Iterator<String> iterator =List.iterator ();  while(Iterator.hasnext ()) {System.out.println (Iterator.next ()); }        if(List = =NULL) {System.out.println ("NULL"); }Else if(List.size () ==0) {System.out.println ("List is not NULL" + "number of elements" +list.size ()); }Else{System.out.println ("Still have elements"); }            }

// output list not a null element number is 0

The difference between the RemoveAll (collection<e> Col) and the clear method of the list collection