Re: compare two byte[] 's

Mark Space wrote:
What does bother me is the lack of utility built into arrays. Changing #equals() or #clone() now would likely be too difficult, but I don't see the harm in adding new methods. All of the very similar overloaded methods in java.util.Arrays, for example, would fit neatly into instance methods of an array class. I honestly can't figure out why this hasn't been done.

This is one possible reason:

Since each array is its own special class, the virtual machine has to synthesize special class objects for arrays. The developers made a choice to keep these objects as small as possible. One thing that could really bloat these objects would be to have to define methods for /every/ single array type.

java.util.Array's toString method has 75 bytes for Object[] and 72 for <primitive>[]. The hashCode methods are between 45 and 56 bytes. The equals methods are between 54 bytes and 78 bytes.

Even ignoring whether or not you want equals to be == or .equals equality, that's 206 bytes for just the bytecode operations for an Object[] class. I'm not including the overhead for method definitions.

I'm willing to bet that the code for Object.clone() special-cases array cloning, just to avoid having to redefine all of these methods.

I'd also imagine that this setup makes the code generation easier: there's only a few bytes that have to be modified, even across primitive and reference type arrays.

--
Beware of bugs in the above code; I have only proved it correct, not tried it. -- Donald E. Knuth
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