T[] ret = (T[]) new Object[size];

Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Comparable;
    at ee.pri.pink.ut.aa.compact.Heap.sort(Heap.java:24)
    at ee.pri.pink.ut.aa.compact.Heap.main(Heap.java:83)