Autoboxing is just a compiler feature. The compiler substitutes it
with say Integer.valueOf(int) and if you take a look at the source of
the Integer class you'll see that it's caching the Integer Objects
from -128 through 127.
Anyways, all three samples are wrong. The new operator will always
create a new Object and == compares only the reference.
Roger
On Jul 9, 2007, at 9:10 PM, Rick Blair wrote:
Actually it goes much deeper than autoboxing. The Java spec
states that a number of instances for primitive wrapper types
must be created. For numeric types I think the values are from
0 to 256 must be included, however the max is up to the JVM
provider. I think this has been true from Java 1.0
Therefore new Integer(0) == new Integer(0) ... new Integer(255) ==
new Integer(255)
Also there is only one new Boolean(true) and one new Boolean(false)
in any given JVM.
Ok I might have lied. It may be on a ClassLoader basis instead of
a JVM basis, but the jist is the same.
Cheers
Rick
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