import java.lang.reflect.*;

/**
 * This program demonstrates the use of reflection for manipulating arrays.
 * @version 1.01 2004-02-21
 * @author Cay Horstmann
 */
public class ArrayGrowTest
{
   public static void main(String[] args)
   {
      int[] a = { 1, 2, 3 };
      a = (int[]) goodArrayGrow(a);
      arrayPrint(a);

      String[] b = { "Tom", "Dick", "Harry" };
      b = (String[]) goodArrayGrow(b);
      arrayPrint(b);

      System.out.println("The following call will generate an exception.");
      b = (String[]) badArrayGrow(b);
   }

   /**
    * This method attempts to grow an array by allocating a new array and copying all elements.
    * @param a the array to grow
    * @return a larger array that contains all elements of a. However, the returned array has 
    * type Object[], not the same type as a
    */
   static Object[] badArrayGrow(Object[] a)
   {
      int newLength = a.length * 11 / 10 + 10;
      Object[] newArray = new Object[newLength];
      System.arraycopy(a, 0, newArray, 0, a.length);
      return newArray;
   }

   /**
    * This method grows an array by allocating a new array of the same type and
    * copying all elements.
    * @param a the array to grow. This can be an object array or a primitive
    * type array
    * @return a larger array that contains all elements of a.
    */
   static Object goodArrayGrow(Object a)
   {
      Class cl = a.getClass();
      if (!cl.isArray()) return null;
      Class componentType = cl.getComponentType();
      int length = Array.getLength(a);
      int newLength = length * 11 / 10 + 10;

      Object newArray = Array.newInstance(componentType, newLength);
      System.arraycopy(a, 0, newArray, 0, length);
      return newArray;
   }

   /**
    * A convenience method to print all elements in an array
    * @param a the array to print. It can be an object array or a primitive type array
    */
   static void arrayPrint(Object a)
   {
      Class cl = a.getClass();
      if (!cl.isArray()) return;
      Class componentType = cl.getComponentType();
      int length = Array.getLength(a);
      System.out.print(componentType.getName() + "[" + length + "] = { ");
      for (int i = 0; i < Array.getLength(a); i++)
         System.out.print(Array.get(a, i) + " ");
      System.out.println("}");
   }
}