Hi Alan, Paul,
Just a comment on comment: wouldn't the variant with a single compute
replace a Package with itself on each repeated call? Semantically it is
the same, but there is a volatile memory store on the cache-hit involved
where in the original variant, it isn't...
On 03/11/2016 05:50 PM, Paul Sandoz wrote:
j.l.ClassLoader
—
1777 // define Package object if the named package is not yet defined
1778 NamedPackage p = packages.computeIfAbsent(name,
1779 k ->
NamedPackage.toPackage(name, m));
1780 if (p instanceof Package)
1781 return (Package)p;
1782
1783 // otherwise, replace the NamedPackage object with Package object
1784 return (Package)packages.compute(name, this::toPackage);
You could merge the computeIfAbsent and compute into a single compute call if
you so wish.
return (Package)packages.compute((n, p) -> {
// define Package object if the named package is not yet defined
if (p == null) return NamedPackage.toPackage(name, m);
// otherwise, replace the NamedPackage object with Package object
return (p instanceof Package) ? p : toPackage(n, p);
});
You could pre-screen the .compute with a .get and this would be the more
optimal (no locking on cache-hits):
NamedPackage p = packages.get(name);
if (p instanceof Package) {
return (Package) p;
}
return (Package)packages.compute((n, p) -> {
// define Package object if it is not yet defined or replace it if it
is a NamedPackage
return (p instanceof Package) ? p : NamedPackage.toPackage(n, m);
});
See, no private ClassLoader.toPackage(String name, NamedPackage p) needed.
If you also care for constant lambda, this could be optimized even
further, but for the price of more complex code:
NamedPackage p = packages.get(name);
if (p instanceof Package) {
return (Package) p;
} else if (p == null) {
Package pkg = NamedPackage.toPackage(name, m);
p = packages.putIfAbsent(name, pkg);
if (p == null) {
return pkg;
}
}
return (Package)packages.compute((n, p) -> {
assert p != null;
// replace NamedPackage with Package
return (p instanceof Package) ? p :
NamedPackage.toPackage(p.name(), p.module());
});
Regards, Peter
