Question

What is the difference between the two :

first :

ArrayList<String> linkList = new ArrayList<String>();

second :

ArrayList linkList = new ArrayList<String>();

Or is there any difference ?

Answer 1

ArrayList<String> linkList = new ArrayList<String>();

uses generics to ensure type safety.

ArrayList linkList = new ArrayList<String>();

doesn’t. As @BruceMartin points out, this means that the lines

linkList.add(0);
String element = (String) linkList.get(0);  

gives a compile time error in the first case, but fails at runtime with the second declaration.

As another example, to get() a String from the two alternatives, the second variant would require a cast:
first:

String element = linkList.get(0);  

second:

String element = (String) linkList.get(0);