Methods have the same type erasure

Question

Hi All, I have this program in my eclipse. And if I compile this with JDK 1.5(build path -> configure build path ->java compilern ->JDK compliance -> compiler compliance level = 1.5), I get the type erasure error for method m1

I have an option of choosing compiler compliance level as 5 in the driop down (build path -> configure build path ->java compilern ->JDK compliance -> compiler compliance level = 5), I don't get this error.

I don't see any difference in this setting I select. But why do I get the error? whats the difference between 1.5 and 5

import java.util.*;   
class  TestWrapper   
{   
public static void main(String[] args) {   
            List<Number> ls1 = new ArrayList<Number>();   
            List<String> ls2 = new ArrayList<String>();   
            m1(ls1,ls2);   
        }   
        public static void m1(List<Integer> l1,List<Integer> l2){}               
      public static void m1(List<Number> l1,List<String> l2)  {}  

Thanks all for the answers Java :)

Answer 1

Java's generics are implemented using a method called "type erasure". Basically, the compiler inserts some hidden casts and removes the type from the generic class's name. So once the code is compiled, List<Integer> becomes List. Same with List<Number> and List<String>. Meaning you'd end up with two public static void m1(List, List) methods.

This shouldn't work in any Java compiler; why it'd be allowed is a bit of a mystery to me.

Answer 2

IMO You should get the error in any case. Can you check what JDK is configured against the compliance level "5"