Tutorial by Examples: me

Introduced in Java 8, default methods are a way of specifying an implementation inside an interface. This could be used to avoid the typical "Base" or "Abstract" class by providing a partial implementation of an interface, and restricting the subclasses hierarchy. Observer patte...

Differences in subsetting syntax A data.table is one of several two-dimensional data structures available in R, besides data.frame, matrix and (2D) array. All of these classes use a very similar but not identical syntax for subsetting, the A[rows, cols] schema. Consider the following data stored i...

<div class="navbar navbar-inverse navbar-fixed-top"> <div class="container"> <div class="navbar-header"> <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".n...

If a covariant type appears as an output, the containing type is covariant. Producing a producer of Ts is like producing Ts. interface IReturnCovariant<out T> { IEnumerable<T> GetTs(); } If a contravariant type appears as an output, the containing type is contravariant. Produc...

Predicates that reason about instantiations are called meta-logical. Examples are: var/1 ground/1 integer/1 These predicates are outside the realm of pure monotonic logic programs, because they break properties like commutativity of conjunction. Other predicates that are meta-logical includ...

In oracle, the difference (in days and/or fractions thereof) between two DATEs can be found using subtraction: SELECT DATE '2016-03-23' - DATE '2015-12-25' AS difference FROM DUAL; Outputs the number of days between the two dates: DIFFERENCE ---------- 89 And: SELECT TO_DATE( '201...

The MEDIAN function since Oracle 10g is an easy to use aggregation function: SELECT MEDIAN(SAL) FROM EMP It returns the median of the values Works on DATETIME values too. The result of MEDIAN is computed by first ordering the rows. Using N as the number of rows in the group, Oracle calcula...

Following code will release the lock. There will be no problem. Behind the scenes lock statement works as try finally lock(locker) { throw new Exception(); } More can be seen in the C# 5.0 Specification: A lock statement of the form lock (x) ... where x is an expression of a referenc...

This example will show you how to create a simple animation using the canvas and the 2D context. It is assumed you know how to create and add a canvas to the DOM and obtain the context // this example assumes ctx and canvas have been created const textToDisplay = "This is an example that uses...

The datetime module can convert a POSIX timestamp to a ITC datetime object. The Epoch is January 1st, 1970 midnight. import time from datetime import datetime seconds_since_epoch=time.time() #1469182681.709 utc_date=datetime.utcfromtimestamp(seconds_since_epoch) #datetime.datetime(2016, 7, 2...

For each environment you need to create a separate appsettings.{EnvironmentName}.json files: appsettings.Development.json appsettings.Staging.json appsettings.Production.json Then open project.json file and include them into "include" in "publishOptions" section. This lis...

Ordered merging of two ordered lists Preserving the duplicates: merge :: Ord a => [a] -> [a] -> [a] merge xs [] = xs merge [] ys = ys merge (x:xs) (y:ys) | x <= y = x:merge xs (y:ys) | otherwise = y:merge (x:xs) ys Top-down version: msort :: Ord a => [...

Bash indirection permits to get the value of a variable whose name is contained in another variable. Variables example: $ red="the color red" $ green="the color green" $ color=red $ echo "${!color}" the color red $ color=green $ echo "${!color}" the ...

{ echo "contents of home directory" ls ~ } > output.txt

import pandas as pd df = pd.DataFrame(np.random.randn(5, 5), columns=list('ABCDE')) To generate various summary statistics. For numeric values the number of non-NA/null values (count), the mean (mean), the standard deviation std and values known as the five-number summary : min: minimum (smal...

Media queries have an optional mediatype parameter. This parameter is placed directly after the @media declaration (@media mediatype), for example: @media print { html { background-color: white; } } The above CSS code will give the DOM HTML element a white background color wh...

<root xmlns="http://test/"> <element xmlns:example="http://foobar/"> <example:hello_world attribute="another example" /> </element> </root> The expression /root will return nothing, because there is no non-namespaced ...

Content has been moved back to the good 'ol JSF wiki page

The most common way to test Angular 2 apps is with the Jasmine test framework. Jasmine allows you to test your code in the browser. Install To get started, all you need is the jasmine-core package (not jasmine). npm install jasmine-core --save-dev --save-exact Verify To verify that Jasmine is...

An example XML file <Sample> <Account> <One number="12"/> <Two number="14"/> </Account> <Account> <One number="14"/> <Two number="16"/> </Account&gt...