Integer a = 200, b = 200;
System.out.println(a < b || a == b || a > b);
System.out.println(a <= b || a > b);
I'm not the type of guy who TYPICALLY likes stuff like that. IMO code used in many java-mind-fucks is just unreal to be found in application written by someone that is not out of his mind ;) But this one posted here I find to be just
lovely :)
If you have your own favorites, post them as a comment :)
Ok, but lest focus on above code sample.
Here is short answer and explanation:
FALSE and TRUE. True because of both `a` and `b` are damn numbers, so it has to be truth no matter what. And false, because: `a` is NOT lower than `b`; `a` is NOT grater then `b` and `a` and `b` are not pointing to the same Intereger object. Cache size is <-128, 127> - check the Integer javadocs if needed.
But that's not all, things can start being interesting from now on. You can actually make both of those sysouts TRUE! How?
Take a look here:
from java.lang.Integer:
/**
* Cache to support the object identity semantics of autoboxing for values between
* -128 and 127 (inclusive) as required by JLS.
*
* The cache is initialized on first usage. The size of the cache
* may be controlled by the -XX:AutoBoxCacheMax=<size> option.
* During VM initialization, java.lang.Integer.IntegerCache.high property
* may be set and saved in the private system properties in the
* sun.misc.VM class.
*/
private static class IntegerCache {
static final int low = -128;
static final int high;
static final Integer cache[];
static {
// high value may be configured by property
int h = 127;
String integerCacheHighPropValue =
sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
if (integerCacheHighPropValue != null) {
int i = parseInt(integerCacheHighPropValue);
i = Math.max(i, 127);
// Maximum array size is Integer.MAX_VALUE
h = Math.min(i, Integer.MAX_VALUE - (-low));
}
high = h;
cache = new Integer[(high - low) + 1];
int j = low;
for(int k = 0; k < cache.length; k++)
cache[k] = new Integer(j++);
}
private IntegerCache() {}
}
It's like mindfuck inside mindfuck - no1 expects this :)
Anyway, empowered with that knowledge, lets hope it's not useless, but alike to
the python paradox. Knowing that little trick does NOT make you a better programmer, but there is a big chance that you ARE already a good programmer if you know about it ;-)
