Collection.toArray() java.lang.ClassCastException

Question

import java.util.HashMap;
import java.util.Map;


public class Main
{
    public static void main(String[] args)
    {
        Map map=new HashMap&l         


        

Answer 1

Use T[] toArray(T[] a) from Collection instead.

Answer 2

toArray() returns an Object[] [and not any object derived from Object[]]. Each element in this array is of type Class, but the array itself is not of type Class[]

You should cast each element in the array to Class instead of trying to cast the array, or use Collection.toArray(T[]) to avoid casting.

Answer 3

Use this code for listing out the values of map i.e. class names:

Object[] array = map.values().toArray();
for (Object object : array) {
    System.out.println(object.toString());
}

Answer 4

Change:

Class[] classes = (Class[]) map.values().toArray();

To:

Class[] classes = map.values().toArray(new Class[0]);

This gives information on which type of array to convert the Collection to. Otherwise, it returns an array of type Object (and that cannot be cast to an Class[]).

---

Quoted from the API documentation for Collection.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. ...
Note that toArray(new Object[0]) is identical in function to toArray().