Java Array Comparison

Question

Working within Java, let's say I have two objects that, thanks to obj.getClass().isArray(), I know are both arrays. Let's further say that I want to compare those two arrays to each other -- possibly by using Arrays.equals. Is there a graceful way to do this without resorting to a big exhaustive if/else tree to figure out which flavor of Arrays.equals needs to be used? I'm looking for something that's less of an eyesore than this:

      if (obj1 instanceof byte[] && obj2 instanceof byte[]) {
         return Arrays.equals((byte[])obj1, (byte[])obj2);
      }
      else if (obj1 instanceof boolean[] && obj2 instanceof boolean[]) {
         ...

Answer 1

You can use reflection.

public static boolean arrayEquals(Object arr1, Object arr2) throws Exception {
    Class<?> c = arr1.getClass();
    if (!c.getComponentType().isPrimitive()) {
        c = Object[].class;
    }
    Method m = Arrays.class.getMethod("equals", c, c);
    return (Boolean) m.invoke(null, arr1, arr2);
}

Reflection is only used to find the right method at run-time without the eyesore you're looking to avoid; the actual Arrays.equals method should run pretty fast.

Obviously production version needs more robust exception handling. You may also want to use deepEquals(Object[], Object[]) instead of equals(Object[], Object[]) for non-primitive arrays.

Answer 2

I'm afraid the only alternative would be to use reflection, which would be nearly as ugly.

Arrays.getClass()
      .getMethod("equals", new Class[]{obj1.getClass(), obj2.getClass()})
      .invoke(null, new object[]{obj1, obj2});

Not tested, could fail in all kinds of ways, needs lots of exception handling...