Exception in thread "main" java.lang.ClassCastException: java.base/java.util.HashMap$Values cannot be cast to java.base/java.util.ArrayList

//直接继承的才可以转型的观点是错误的,不好意思,误导了. 比如:
        Collection<Integer> c = new ArrayList<>();
        ArrayList<Integer>  list = (ArrayList<Integer>) c;
//        继承关系:
//        java.util.AbstractCollection<E>
//        java.util.AbstractList<E>
//        java.util.ArrayList<E
//        这个装换是没有问题的

       Animal  animal = new Dog();
       Animal animal1 = new Cat();
       Cat cat = (Cat)animal;
 //        Exception in thread "main" java.lang.ClassCastException: test.Dog cannot be cast to test.Cat

//       同样的例子 :
       Collection<Integer> values = new HashMap<Integer,Integer>().values();
       ArrayList<Integer> list1 =(ArrayList<Integer>) values;
//       　 输出:Exception in thread "main" java.lang.ClassCastException: java.base/java.util.HashMap$Values cannot be cast to java.base/java.util.ArrayList
//
//　　　　大概意思就是  HashMap的内部类Values(狗)不能装换成 HashMap(猫)

源码:

 
public Collection<V> values() {
        Collection<V> vs = values;
        if (vs == null) {
            vs = new Values();
            values = vs;
        }
        return vs;
    }

final class Values extends AbstractCollection<V> {
        public final int size()                 { return size; }
        public final void clear()               { HashMap.this.clear(); }
        public final Iterator<V> iterator()     { return new ValueIterator(); }
        public final boolean contains(Object o) { return containsValue(o); }
        public final Spliterator<V> spliterator() {
            return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
        }
        public final void forEach(Consumer<? super V> action) {
            Node<K,V>[] tab;
            if (action == null)
                throw new NullPointerException();
            if (size > 0 && (tab = table) != null) {
                int mc = modCount;
                for (Node<K,V> e : tab) {
                    for (; e != null; e = e.next)
                        action.accept(e.value);
                }
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }
    }
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