Question

I have classes as below.

public interface ITest <T>
{
   public Set<T> methodHere();
}

public class test1 implements ITest<String>
{
   Set<String> methodHere(){
      return // Set of String
   }
}

public class test2 implements ITest<Integer>
{
   Set<Integer> methodHere(){
     return // Set of Integer
   }
}

public class ITestFactory {
 public static ITest getInstance(int type) {
  if(type == 1) return new test1();
  else if(type == 2) return new test2();
 }
}
public class TestUser {
    public doSomething(int type) {
       ITest t = ITestFactory.getInstance(type);
       if(type == 1) Set<Integer> i = t.methodHere();
       else if(type == 2) Set<String> s = t.methodHere();
       ...
    }
}

There is a warning in the factory class that ITest is used as raw type. What modification should I do to get rid of it?

The TestUser code looks ugly. Am I missing something very basic? I don’t want to use Set<?>

Thanks
Nayn

Answer 1

You can return a ITest<?> to get rid of the warning but probably you want a more strongly type aproach:

public class TestFactory {
   public static ITest<?> getInstance(int type) {
      if(type == 1) 
         return new test1();
      else if(type == 2) 
         return new test2();
      else
         throw new IllegalArgumentException("Unknown type");
   }

   public static <T> ITest<T> getInstance(Class<T> clazz) {
      if(clazz == String.class) 
         return new test1();
      else if(clazz == Integer.class) 
         return new test2();
      else 
         throw new IllegalArgumentException("Unknown type");
   }
}