为什么这段代码抛出异常

Question

    HashMap h = new HashMap();
    Collection c = h.values();
    Object[] a = c.toArray();
    LinkedList<Object[]> l = new LinkedList<Object[]>();
    l.addFirst(a);
    TreeSet<Object[]> t = new TreeSet<Object[]>(l); //throws ClassCastException exception

因为我没有违反任何合同，所以这个异常很奇怪。

Answer 1

TreeSet 构造函数抛出 ClassCastException if a collection is passed whose elements do not all implement Comparable. Object[] does not implement Comparable。

详情请参阅constructor reference。

ClassCastException - if the elements in c are not Comparable, or are not mutually comparable NullPointerException - if the specified collection is null

为什么这段代码抛出异常

Why does this code throws exception

java

classcastexception