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Java generics - why is “extends T” allowed but not “implements T”?
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To add to the confusion getFoo(List<? super Foo> fooList) ONLY works with the class that literally are extended by Foo like class Foo extends WildcardClass. In this case a List<WildcardClass> would be acceptable input. However any class...
Java Enum definition
...? By making the type argument the new type itself. So if I've got an enum called StatusCode, it would be equivalent to:
public class StatusCode extends Enum<StatusCode>
Now if you check the constraints, we've got Enum<StatusCode> - so E=StatusCode. Let's check: does E extend Enum<S...
regex for matching something if it is not preceded by something else
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You want to use negative lookbehind like this:
\w*(?<!foo)bar
Where (?<!x) means "only if it doesn't have "x" before this point".
See Regular Expressions - Lookaround for more information.
Edit: added the \w* to capture the characters before (e.g. "beach").
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Is key-value observation (KVO) available in Swift?
...Object subclass. Consider that you wanted to observe the bar property of a Foo class. In Swift 4, specify bar as dynamic property in your NSObject subclass:
class Foo: NSObject {
@objc dynamic var bar = 0
}
You can then register to observe changes to the bar property. In Swift 4 and Swift 3.2...
how to restart only certain processes using supervisorctl?
...rvisor.rpcinterface:make_main_rpcinterface
supervisorctl command can be called with a group name:
supervisorctl restart foo:
as well as with multiple process names:
supervisorctl restart foo:cat1 cat2
share
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Difference between Hive internal tables and external tables?
...r node it uses to keep track of state.
For instance, when you CREATE TABLE FOO(foo string) LOCATION 'hdfs://tmp/';, this table schema is stored in the database.
If you have a partitioned table, the partitions are stored in the database(this allows hive to use lists of partitions without going to th...
Declare multiple module.exports in Node.js
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module.js:
const foo = function(<params>) { ... }
const bar = function(<params>) { ... }
//export modules
module.exports = {
foo,
bar
}
main.js:
// import modules
var { foo, bar } = require('module');
// pass your p...
ORA-00979 not a group by expression
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You must put all columns of the SELECT in the GROUP BY or use functions on them which compress the results to a single value (like MIN, MAX or SUM).
A simple example to understand why this happens: Imagine you have a database like this:
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Should I pass an std::function by const-reference?
...rmance, pass by value if you are storing it.
Suppose you have a function called "run this in the UI thread".
std::future<void> run_in_ui_thread( std::function<void()> )
which runs some code in the "ui" thread, then signals the future when done. (Useful in UI frameworks where the UI ...
Read lines from a file into a Bash array [duplicate]
... from BinaryZebra's comment
and tested here. The addition of command eval allows for the expression to be kept in the present execution environment while the expressions before are only held for the duration of the eval.
Use $IFS that has no spaces\tabs, just newlines/CR
$ IFS=$'\r\n' GLOBIGNORE=...