Tutorial by Examples: a

Using ThreadLocal

A useful tool in Java Concurrency is ThreadLocal – this allows you to have a variable that will be unique to a given thread. Thus, if the same code runs in different threads, these executions will not share the value, but instead each thread has its own variable that is local to the thread. For exa...

Java Language • Concurrent Programming (Threads)

Setext-Style Headers

To create a first-level (<h1>) header, use the equal sign (=) in a line under your text: All About Dogs ============== All About Dogs Use hyphens (-) for second-level (<h2>) headers: The Debut Novel --------------- The Debut Novel The line below the header can be of a...

Markdown • Headers

Margin Collapsing

When two margins are touching each other vertically, they are collapsed. When two margins touch horizontally, they do not collapse. Example of adjacent vertical margins: Consider the following styles and markup: div{ margin: 10px; } <div> some content </div> <div&gt...

CSS • Margins

Global variable best practices

We can illustrate this problem with the following pseudo-code function foo() { global $bob; $bob->doSomething(); } Your first question here is an obvious one Where did $bob come from? Are you confused? Good. You've just learned why globals are confusing and considered a bad p...

PHP • Variables

What is Bool?

Bool is a Boolean type with two possible values: true and false. let aTrueBool = true let aFalseBool = false Bools are used in control-flow statements as conditions. The if statement uses a Boolean condition to determine which block of code to run: func test(_ someBoolean: Bool) { if som...

Swift Language • Booleans

Negate a Bool with the prefix ! operator

The prefix ! operator returns the logical negation of its argument. That is, !true returns false, and !false returns true. print(!true) // prints "false" print(!false) // prints "true" func test(_ someBoolean: Bool) { if !someBoolean { print("someBoolean ...

Swift Language • Booleans

Creating Arrays

Creating immutable arrays: NSArray *myColors = [NSArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; // Using the array literal syntax: NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; ...

Objective-C Language • NSArray

Finding out the Number of Elements in an Array

NSArray *myColors = [NSArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; NSLog (@"Number of elements in array = %lu", [myColors count]);

Objective-C Language • NSArray

Adding elements

NSMutableArray *myColors; myColors = [NSMutableArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; [myColors addObject: @"Indigo"]; [myColors addObject: @"Violet"]; //Add objects from an NSArray NSArray *myArray = @[@...

Objective-C Language • NSMutableArray

Accessing elements

NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; // Preceding is the preferred equivalent to [NSArray arrayWithObjects:...] Getting a single item The objectAtIndex: method provides a single object. The first object in an NSArray is index 0. Si...

Objective-C Language • NSArray

Sorting Arrays

NSMutableArray *myColors = [NSMutableArray arrayWithObjects: @"red", @"green", @"blue", @"yellow", nil]; NSArray *sortedArray; sortedArray = [myColors sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];

Objective-C Language • NSMutableArray

Spanning columns or rows

Table cells can span multiple columns or rows using the colspan and rowspan attributes. These attributes can be applied to <th> and <td> elements. <table> <tr> <td>row 1 col 1</td> <td>row 1 col 2</td> <td>row 1 c...

HTML • Tables

Element Language

The lang attribute is used to specify the language of element content and attribute text values: <p lang="en">The content of this element is in English.</p> <p lang="en" title="The value of this attribute is also in English.">The content of this el...

HTML • Content Languages

Elements with Multiple Languages

You can "overwrite" a language declaration: <p lang="en">This English sentence contains the German word <span lang="de">Hallo</span>.</p>

HTML • Content Languages

Handling Attributes with Different Languages

You can "overwrite" a parent element's language declaration by introducing any element apart from applet, base, basefont, br, frame, frameset, hr, iframe, meta, param, script (of HTML 4.0) with an own lang attribute: <p lang="en" title="An English paragraph"> ...

HTML • Content Languages

Base Document Language

It’s a good practice to declare the primary language of the document in the html element: <html lang="en"> If no other lang attribute is specified in the document, it means that everything (i.e., element content and attribute text values) is in that language. If the document con...

HTML • Content Languages

params

params allows a method parameter to receive a variable number of arguments, i.e. zero, one or multiple arguments are allowed for that parameter. static int AddAll(params int[] numbers) { int total = 0; foreach (int number in numbers) { total += number; } ret...

C# Language • Keywords

Simple usage

Object initializers are handy when you need to create an object and set a couple of properties right away, but the available constructors are not sufficient. Say you have a class public class Book { public string Title { get; set; } public string Author { get; set; } // the rest o...

C# Language • Object initializers

Usage with anonymous types

Object initializers are the only way to initialize anonymous types, which are types generated by the compiler. var album = new { Band = "Beatles", Title = "Abbey Road" }; For that reason object initializers are widely used in LINQ select queries, since they provide a convenie...

C# Language • Object initializers

Recurse the whole pattern

The construct (?R) is equivalent to (?0) (or \g<0>) - it lets you recurse the whole pattern: <(?>[^<>]+|(?R))+> This will match properly balanced angle brackets with any text in-between the brackets, like <a<b>c<d>e>.

Regular Expressions • Recursion