[java 1 vs. java 2 comments]
: Has there been any documentation out about this? I don't see why using the
: Collections API would increase performance.
Yes, a number of articles and book chapters have been written about
the cost of acquiring the synchronization lock on java objects. Since
every method on Vector/Hashtable is synchronized, and since these were
frequently used classes in JDK < 1.2, they quickly become performance
bottlenecks. The java 2 collections are not synchronized by default
and so do not suffer from this particular shortcoming.
The second performance problem I noticed is algorithmic in nature.
The JDE builds a list of all compiled classes in your project (>
5,000 in the JDK base -- not counting i18n and so forth -- alone).
When determining which class to import, it does a linear scan on this
list. Clearly it would be faster to sort the list and then use binary
searches for lookups.
Other obvious, low hanging fruit include using StringBuffer.append()
instead of String concatenation inside of loops, and removing unnecessary
synchronized method calls in those same loops.
An alternative to using a sort/search loop algorithm would be to replace
the list data structure with a Map. In the current implementation, the
list is comprised of fully qualified classnames. The search looks for
the qualified classname only (the `Map' in `java.util.Map'). Clearly one
could precompute the `Map' string when building the data structure and
turn the search loop into a simple hash lookup that resolves to either
a single String (`Map' -> `java.util.Map') or a List of Strings (`List'
-> {`java.util.List', `java.awt.List'}).
Eric
