block5.java

List<Integer> intList = new ArrayList<>();
List<Double> doubleList = new ArrayList<>();
List<Number> numList = new ArrayList<>();
List<Object> objList = new ArrayList<>();

List<? extends Number> extends1 = intList;
List<? extends Number> extends2 = doubleList;
List<? extends Number> extends3 = numList;
List<? extends Number> extends4 = objList; // Error: incompatible types

List<? super Number> super1 = intList; // Error: incompatible types
List<? super Number> super2 = doubleList; // Error: incompatible types
List<? super Number> super3 = numList;
List<? super Number> super4 = objList;