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Difference between HashSet and HashMap?
... functions. This is critical because HashMap uses power-of two length hash tables." weblogs.java.net/blog/2005/06/18/hashmap-implementation - however, if you look at the doc you'll see that this hash distributes things over "buckets", so in the end I believe two things can get mapped the same bucket...
Multiple queries executed in java in single statement
... it is possible to execute something like this using JDBC.
"SELECT FROM * TABLE;INSERT INTO TABLE;"
Yes it is possible. There are two ways, as far as I know. They are
By setting database connection property to allow multiple queries,
separated by a semi-colon by default.
By calling a stored pro...
What's the idiomatic syntax for prepending to a short python list?
...ort is an exception, making deque definitively not entirely Liskov substitutable for list.
>>> set(dir(list)) - set(dir(deque))
{'sort'}
The deque also has an appendleft method (as well as popleft). The deque is a double-ended queue and a doubly-linked list - no matter the length, it al...
MySQL ON DUPLICATE KEY UPDATE for multiple rows insert in single query
...r.
for SQL server, the way to work around this is to first declare a temp table, insert value to that temp table, and then use MERGE
Like this:
declare @Source table
(
name varchar(30),
age decimal(23,0)
)
insert into @Source VALUES
('Helen', 24),
('Katrina', 21),
('Samia', 22),
('Hui Ling', 25)...
Remove data.frame row names when using xtable
...and I assume it's quite easy too. I'm writing a report and I want to use xtable package for LaTeX table generation (note that memisc package does the job, but say I want to do this solely with xtable ).
...
In Java, how do I convert a byte array to a string of hex digits while keeping leading zeros? [dupli
...ne takes every 4-bit nibble and turns it into a hex char. And it's using a table lookup, so it's probably fast. It could probably be faster if you replace v/16 and v%16 with bitwise shifts and AND's, but I'm too lazy to test it right now.
...
Why do we use arrays instead of other data structures?
...1000 compared to getting to P4.
Higher level data structures, such as hashtables, stacks and queues, all may use an array (or multiple arrays) internally, while Linked Lists and Binary Trees usually use nodes and pointers.
You might wonder why anyone would use a data structure that requires linear...
How can I avoid Java code in JSP files, using JSP 2?
...fway, all you get is a blank page.
Testability: scriptlets are not unit-testable.
Maintainability: per saldo more time is needed to maintain mingled/cluttered/duplicated code logic.
Sun Oracle itself also recommends in the JSP coding conventions to avoid use of scriptlets whenever the same functio...
Increment a value in Postgres
...res. I want to take a value (which is an integer) in a field in a postgres table and increment it by one. For example if the table 'totals' had 2 columns, 'name' and 'total', and Bill had a total of 203, what would be the SQL statement I'd use in order to move Bill's total to 204?
...
Laravel orderBy on a relationship
... Nope. I have tried this, it doesn't work. Here's my case : I have two table (appointments and schedules), the query is simple : get appointments order by schedules.datetime descending. I have solution by adding new column in table appointments to store datetime from table schedules. And now I o...