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

Answer 1

you can use the enum strategy pattern to create a comparator for each type:

public enum ArrayEq {
    BYTE_PRIMITIVE(Byte.TYPE) {
        protected boolean doEquals(Object array1, Object array2) {
            return Arrays.equals((byte[]) array1, (byte[]) array2);
        }
    },
    ... enum element for each component type

   private final Class type;

   private ArrayEq(final Class type) { this.type = type; }
   public Class getComponentType() { return type; }

   // force all enums to implement this method
   protected abstract boolean doEquals(Object array1, Object array2);

   public static boolean equals(Object array1, Object array2) {
       if(array1 == null) return array2 == null;

       // you need to populate this map in a static initializer of the enum
       // a simple linear search would work too since the number of elements is small
       typeToElementMap.get(array1.getComponentType())
           .doEquals(array1, array2);
   }

}

Error handling omitted, but of course, you want to throw IllegalArgumentException wherever incorrect types are passed around (I prefer to let ClassCastException be JVM generated, and throw IAE in my own code when I detect something wrong).