Storing a value in an array at run time causes a check that the type stored is compatible with the element type of the array.

The code below compiles without errors, but when it is run we get:

Exception in thread "main" java.lang.ArrayStoreException:
      java.lang.Integer
      at ex3.main(ex3.java:10)

   

    1   public class ex3
    2   {
    3     
    4     public static void main(String[] args)
    5     {
    6       Object[] s = new String[3];  // A String is an Object
    7   
    8       s[0] = "hello";
    9       s[1] = "goodbye";
   10       s[2] = new Integer(42);      // An Integer is an Object, but is not a String
   11   
   12       for(int i = 0; i < s.length; i++) {
   13         System.out.println(s[i]);
   14       }
   15     }
   16   
   17   }