Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer；

标签：java   cast   

public class Test {

    public static void main(String[] args) {
        System.out.println(new CountingGenerator.String(12).next());
        List<Integer> list=new ArrayList<Integer>();
        list.add(new Integer(1));
        list.add(new Integer(2));

        Integer[] c = {1,3,3};
        //throw an exception:
        c = (Integer[]) list.toArray();
    }
}

I wonder why this happened ? Integer is a subclass of Object,so it should be Ok instead! please answer me deeply! I want know why? what‘s the principle ?

回答：

up vote3down voteunaccept

Change the line c=(Integer[]) list.toArray(); to c= list.toArray(c); // add c as parameter In your list.toArray(); returns Object[] and JVM doesn‘t know how to blindly downcast Object[]to Integer[]. public Object[] toArray() //return Object type array public <T> T[] toArray(T[] a) //Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array Java Docs shareedit edited 20 hours ago answered 21 hours ago singhakash 1,9931118

Ljava.lang.Object; cannot be cast to [Ljava.lang.Integer；

标签：java   cast   

原文地址：http://blog.csdn.net/lemon89/article/details/44727013