4 ms·

I just went to post that... can anybody explain to me what exactly is going on? I'm not familiar with Groovy, and I try to forget Java when I can, but this just

by jff 16y ago

I just went to post that... can anybody explain to me what exactly is going on? I'm not familiar with Groovy, and I try to forget Java when I can, but this just plain doesn't make any sense.

akronim 16y ago
They're aiming for compatibility with Java 1.4, which doesn't have varargs. In java 1.5 you could just write public static Object[] createArray(Object... args) { return args; }
- abp 16y ago
  So just another missing line of essential commentary?
- zmmmmm 16y ago
  I remember discovering this and deciding to eliminate it as part of an effort to compress the groovy jar file a bit more (long story, but basically I was running some Groovy in an applet, every byte counts). I thought I'd found a jackpot and that killing this class would surely eliminate a nice chunk of byte code. To my amazement it makes almost no difference. With pack200 the redundancy of all these methods is totally stripped out. It took me an hour or so of work and I think it made less than 200 bytes difference in the end.
riffraff 16y ago
well, java has variable length arguments now so the whole file could be simply public static Object[] createArray() { return EMPTY; } public static Object[] createArray(Object... args) { return args; } My guess is they probably had this before java supported such a syntax so that you could create arrays easily. once you auto-generate the file, you just do it up to 255. I do not have a good explanation of why this is better than the normal array initializer though, apart from the fact that once you standardize on this you may have some minimal advantage in not allocating empty arrays around.
- lepht 16y ago
  >My guess is they probably had this before java supported such a syntax so that you could create arrays easily varargs came in Java 1.5, September 30, 2004 Groovy 1.0, January 2, 2007 Definitely could be for compiler optimizations or backwards compatibility, just providing some context for any possible historical reasons like the one you stated.
  - bruceboughton 16y ago
    If it's for optimisation, why introduce another method call (ArrayUtil.createArray) instead of using new Object[] { .. } directly? I can understand the backwards compatibility argument, but I just don't see the need for this ArrayUtil class.
    - lepht 16y ago
      Two things: Calling new Object[]{} directly is going to call the constructor for Object anyway, so there's no really difference in the number of method calls for either. Also, in terms of optimization: calling new Object[]{...} makes it so that the size of the array isn't known until runtime when the initialization parameters can be evaluated. Because array length is immutable the JVM must wait until execution to create an array of the proper size. With the overloaded static createArray() methods used in ArrayUtils the size of the array can be determined and memory allocated (based on the number of parameters at the callsite and hence which variation of the method should be called) at the JRE's convenience/when optimal. All of this is probably micro-optimization to the who-really-cares level, and might even be irrelevant due to javac/JIT magic, just wanted to show that the existence of the new Object[] syntax doesn't preclude there being performance gains from using something like ArrayUtil.createArray().
  - GrandMasterBirt 16y ago
    Compatibility :) In any case, you can easily generate an ant script or whatever build groovy uses to either generate the vararg code or the insaneo source code as we see here. The point being that this should only happen when compiling groovy for java 1.4.
nysauhem 16y ago
You could accomplish the same thing with a public static Object[] createArray(Object... objects) { ... } but doing it statically, hard-coded like this is faster. You leave it to the compiler to determine the length of the arguments, rather than having to count them at run-time. The Google Guava library does something similar, but not to this extent, only up to 12 args http://guava-libraries.googlecode.com/svn-history/r12/trunk/javadoc/com/google/common/collect/ImmutableList.html http://guava-libraries.googlecode.com/svn-history/r12/trunk/...

by jff 16y ago

I just went to post that... can anybody explain to me what exactly is going on? I'm not familiar with Groovy, and I try to forget Java when I can, but this just plain doesn't make any sense.

akronim 16y ago

They're aiming for compatibility with Java 1.4, which doesn't have varargs. In java 1.5 you could just write public static Object[] createArray(Object... args) { return args; }

abp 16y ago
So just another missing line of essential commentary?
zmmmmm 16y ago
I remember discovering this and deciding to eliminate it as part of an effort to compress the groovy jar file a bit more (long story, but basically I was running some Groovy in an applet, every byte counts). I thought I'd found a jackpot and that killing this class would surely eliminate a nice chunk of byte code. To my amazement it makes almost no difference. With pack200 the redundancy of all these methods is totally stripped out. It took me an hour or so of work and I think it made less than 200 bytes difference in the end.

riffraff 16y ago

well, java has variable length arguments now so the whole file could be simply public static Object[] createArray() { return EMPTY; } public static Object[] createArray(Object... args) { return args; } My guess is they probably had this before java supported such a syntax so that you could create arrays easily. once you auto-generate the file, you just do it up to 255. I do not have a good explanation of why this is better than the normal array initializer though, apart from the fact that once you standardize on this you may have some minimal advantage in not allocating empty arrays around.

lepht 16y ago
>My guess is they probably had this before java supported such a syntax so that you could create arrays easily varargs came in Java 1.5, September 30, 2004 Groovy 1.0, January 2, 2007 Definitely could be for compiler optimizations or backwards compatibility, just providing some context for any possible historical reasons like the one you stated.
- bruceboughton 16y ago
  If it's for optimisation, why introduce another method call (ArrayUtil.createArray) instead of using new Object[] { .. } directly? I can understand the backwards compatibility argument, but I just don't see the need for this ArrayUtil class.
  - lepht 16y ago
    Two things: Calling new Object[]{} directly is going to call the constructor for Object anyway, so there's no really difference in the number of method calls for either. Also, in terms of optimization: calling new Object[]{...} makes it so that the size of the array isn't known until runtime when the initialization parameters can be evaluated. Because array length is immutable the JVM must wait until execution to create an array of the proper size. With the overloaded static createArray() methods used in ArrayUtils the size of the array can be determined and memory allocated (based on the number of parameters at the callsite and hence which variation of the method should be called) at the JRE's convenience/when optimal. All of this is probably micro-optimization to the who-really-cares level, and might even be irrelevant due to javac/JIT magic, just wanted to show that the existence of the new Object[] syntax doesn't preclude there being performance gains from using something like ArrayUtil.createArray().
- GrandMasterBirt 16y ago
  Compatibility :) In any case, you can easily generate an ant script or whatever build groovy uses to either generate the vararg code or the insaneo source code as we see here. The point being that this should only happen when compiling groovy for java 1.4.

nysauhem 16y ago

You could accomplish the same thing with a public static Object[] createArray(Object... objects) { ... } but doing it statically, hard-coded like this is faster. You leave it to the compiler to determine the length of the arguments, rather than having to count them at run-time. The Google Guava library does something similar, but not to this extent, only up to 12 args http://guava-libraries.googlecode.com/svn-history/r12/trunk/javadoc/com/google/common/collect/ImmutableList.html http://guava-libraries.googlecode.com/svn-history/r12/trunk/...