=== pkg/Converter.java ===
package pkg;

public interface Converter<T> {
  T convert(String input);
}

=== pkg/EnumConverter.java ===
package pkg;

public abstract class EnumConverter<T extends Enum<T>> implements Converter<T> {
  @Override public T convert(String input) { return null; }
}

=== pkg/Suite.java ===
package pkg;

public enum Suite {
  HEARTS
}

=== pkg/Test.java ===
package pkg;

public class Test {
  public static class MyConverter extends EnumConverter<Suite> {
  }
}