Question

Well the question says it all. Heres an Example of what i want

String s = new String();
List<s.type> ls = new ArrayList<s.type>();

Something like that, or any elegant way to achieve this, please no multiple if conditions or condition logic, as there may be unlimited data types, i have used string here only as an example, it can be anything.

Answer 1

If I understood you correctly, you want to know the class (type) of an instance (object) in runtime (existing), which has nothing to do with generics though, as Petr explained.

public class Types {    
 public static void main(String[] args) {
     String s = "";
     Runtime r = Runtime.getRuntime();
     Types t = new Types();

     List<Class> types = new LinkedList<Class>();         
     types.add(Integer.class);
     types.add(t.getClass());
     types.add(r.getClass());
     types.add(s.getClass());

     for (Class type :types) {
         System.out.println(type.getSimpleName());
     }         
 }    
}

which outputs:

Integer
Types
Runtime
String

However, such approach is rarely needed, so rethink is there a simpler solution to your problem. If you still want to tackle it like this:

• What is reflection, and why is it useful?
• official tutorial

EDIT:

The other interpretation of your question leads to a dynamic generic list as answer:

public static <T> List<T> createListOfType() {
    return new ArrayList<T>();
}

public static void main(String[] args) {
    List<String> a = createListOfType();    
    List<Integer> b = createListOfType();
    a.add("");
    b.add(2);
    a.add(2); // remove this line to compile
    b.add(""); // remove this line to compile       
}