raw-types

I'm currently working on a port of a jEdit plugin to write all code in Scala. However Im forced at a certain point to implement my own Comparator. My simplified code is as follows: class compare extends MiscUtilities.Compare { def compare(obj1: AnyRef, obj2: AnyRef): Int = 1 } The MiscUtilities.Compare has the following signature when looking from IntelliJ public static interface Compare extends java.util.Comparator { int compare(java.lang.Object o, java.lang.Object o1); } However when im trying to compile my class I get a error saying: error: class compare needs to be abstract, since method

This question already has an answer here: Cannot convert from List<List> to List<List<?>> 3 answers I did not get this code to compile either way: List<List> a = new ArrayList(); List<List<?>> b = new ArrayList(); a = b; // incompatible types b = a; // incompatible types It seems that java does not consider List and List<?> to be the same type when it comes to generics. Why is that? And is there some nice way out? Context There is a library function with following signature: public <T> Set<Class<? extends T>> getSubTypesOf(final Class<T> type) . This works fine for simple types passed as

I want to define a class that implements the generic Comparable interface. While in my class I also defined a generic type element T . In order to implement the interface, I delegate the comparison to T . Here is my code: public class Item<T extends Comparable<T>> implements Comparable<Item> { private int s; private T t; public T getT() { return t; } @Override public int compareTo(Item o) { return getT().compareTo(o.getT()); } } When I try to compile it, I get the following error information: Item.java:11: error: method compareTo in interface Comparable<T#2> cannot be applied to given types;