Tutorial by Examples: b

Java provides, as part of the utils package, a basic pseudo-random number generator, appropriately named Random. This object can be used to generate a pseudo-random value as any of the built-in numerical datatypes (int, float, etc). You can also use it to generate a random Boolean value, or a random...

The method nextInt(int bound) of Random accepts an upper exclusive boundary, i.e. a number that the returned random value must be less than. However, only the nextInt method accepts a bound; nextLong, nextDouble etc. do not. Random random = new Random(); random.nextInt(1000); // 0 - 999 int num...

By default error message appears below textbox in <div class="help-block"></div> on keyUp or after pressing submit button if any validation constraints aren't met. Sometimes we want a message on submit only i.e. no validation at onKeyup event. Let's check yii2/widgets/ActiveF...

A Kotlin interface contains declarations of abstract methods, and default method implementations although they cannot store state. interface MyInterface { fun bar() } This interface can now be implemented by a class as follows: class Child : MyInterface { override fun bar() { ...

Java 8 provides classes called IntSummaryStatistics, DoubleSummaryStatistics and LongSummaryStatistics which give a state object for collecting statistics such as count, min, max, sum, and average. Java SE 8 List<Integer> naturalNumbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); IntSu...

What is recursion: In general, recursion is when a function invokes itself, either directly or indirectly. For example: // This method calls itself "infinitely" public void useless() { useless(); // method calls itself (directly) } Conditions for applying recursion to a probl...

The double-negation !! is not a distinct JavaScript operator nor a special syntax but rather just a sequence of two negations. It is used to convert the value of any type to its appropriate true or false Boolean value depending on whether it is truthy or falsy. !!1 // true !!0 ...

If a name is bound inside a function, it is by default accessible only within the function: def foo(): a = 5 print(a) # ok print(a) # NameError: name 'a' is not defined Control flow constructs have no impact on the scope (with the exception of except), but accessing variable that w...

enum MyEnum { One, Two, Three } foreach(MyEnum e in Enum.GetValues(typeof(MyEnum))) Console.WriteLine(e); This will print: One Two Three

Running the latest Liferay CE is straightforward: Go to https://www.liferay.com/downloads. Choose a bundle among the ones listed. For beginners, the Tomcat bundle is a good choice. Click in "Download." Unzip the download package whenever you find fit. The unzipped directory will...

One of the main differences between lists and tuples in Python is that tuples are immutable, that is, one cannot add or modify items once the tuple is initialized. For example: >>> t = (1, 4, 9) >>> t[0] = 2 Traceback (most recent call last): File "<stdin>", l...

You can use a column's number (where the leftmost column is '1') to indicate which column to base the sort on, instead of describing the column by its name. Pro: If you think it's likely you might change column names later, doing so won't break this code. Con: This will generally reduce readabilit...

<input type="button" value="Button Text"> Buttons can be used for triggering actions to occur on the page, without submitting the form. You can also use the <button> element if you require a button that can be more easily styled or contain other elements: <butt...

Substitutability is a principle in object-oriented programming introduced by Barbara Liskov in a 1987 conference keynote stating that, if class B is a subclass of class A, then wherever A is expected, B can be used instead: class A {...} class B extends A {...} public void method(A obj) {...} ...

A button can be disabled by Swift myButton.isEnabled = false Objective-C: myButton.enabled = NO; The button will become gray: If you don't want the button appearance to change when disabled set adjustsImageWhenDisabled to false / NO

Swift label.backgroundColor = UIColor.redColor() label.backgroundColor = .redColor() Swift 3 label.backgroundColor = UIColor.red Objective-C label.backgroundColor = [UIColor redColor];

manifest.json gives information about the extension, such as the most important files and the capabilities that the extension might use. Among the supported manifest fields for extensions, the following three are required. { "manifest_version": 2, "name": "My Exte...

Suppose you have defined the following Person class: public class Person { String name; int age; public Person (int age, String name) { this.age = age; this.name = name; } } If you instantiate a new Person object: Person person = new Person(25, &qu...

There are 4 looping constructs in Rust. All examples below produce the same output. Infinite Loops let mut x = 0; loop { if x > 3 { break; } println!("{}", x); x += 1; } While Loops let mut x = 0; while x <= 3 { println!("{}", x); x += 1; ...

As mentioned in Basics, we can use anything which implements IntoIterator with the for loop: let vector = vec!["foo", "bar", "baz"]; // vectors implement IntoIterator for val in vector { println!("{}", val); } Expected output: foo bar baz ...