Tutorial by Examples: sin

OptionalDouble, OptionalInt and OptionalLong work like Optional, but are specifically designed to wrap primitive types: OptionalInt presentInt = OptionalInt.of(value); OptionalInt absentInt = OptionalInt.empty(); Because numeric types do have a value, there is no special handling for null. Empt...

Enum can be considered to be syntax sugar for a sealed class that is instantiated only a number of times known at compile-time to define a set of constants. A simple enum to list the different seasons would be declared as follows: public enum Season { WINTER, SPRING, SUMMER, FA...

An enum can contain a method, just like any class. To see how this works, we'll declare an enum like this: public enum Direction { NORTH, SOUTH, EAST, WEST; } Let's have a method that returns the enum in the opposite direction: public enum Direction { NORTH, SOUTH, EAST, WEST; ...

One use of SharedPreferences is to implement a "Settings" screen in your app, where the user can set their preferences / options. Like this: A PreferenceScreen saves user preferences in SharedPreferences. To create a PreferenceScreen, you need a few things: An XML file to define the av...

Scanner scanner = new Scanner(System.in); //Scanner obj to read System input String inputTaken = new String(); while (true) { String input = scanner.nextLine(); // reading one line of input if (input.matches("\\s+")) // if it matches spaces/tabs, stop reading b...

Scanner scanner = null; try { scanner = new Scanner(new File("Names.txt")); while (scanner.hasNext()) { System.out.println(scanner.nextLine()); } } catch (Exception e) { System.err.println("Exception occurred!"); } finally { if (scanner != nul...

Here we have a class Counter with methods countNumbers() and hasNumbers(). public class Counter { /* To count the numbers in the input */ public static int countNumbers(String input) { int count = 0; for (char letter : input.toCharArray()) { if (Character....

add() and roll() can be used to increase/decrease Calendar fields. Calendar calendar = new GregorianCalendar(2016, Calendar.MARCH, 31); // 31 March 2016 The add() method affects all fields, and behaves effectively if one were to add or subtract actual dates from the calendar calendar.add(Calend...

When desired XML format differs from Java object model, an XmlAdapter implementation can be used to transform model object into xml-format object and vice versa. This example demonstrates how to put a field's value into an attribute of an element with field's name. public class XmlAdapterExample { ...

"External" Storage is another type of storage that we can use to save files to the user's device. It has some key differences from "Internal" Storage, namely: It is not always available. In the case of a removable medium (SD card), the user can simply remove the storage. It i...

The shared remote interface: package remote; import java.rmi.Remote; import java.rmi.RemoteException; public interface RemoteServer extends Remote { int stringToInt(String string) throws RemoteException; } The server implementing the shared remote interface: package server; im...

Classes implementing Iterable<> interface can be used in for loops. This is actually only syntactic sugar for getting an iterator from the object and using it to get all elements sequentially; it makes code clearer, faster to write end less error-prone. public class UsingIterable { pub...

While using the foreach loop (or "extended for loop") is simple, it's sometimes beneficial to use the iterator directly. For example, if you want to output a bunch of comma-separated values, but don't want the last item to have a comma: List<String> yourData = //... Iterator<Str...

You can use Scanner to read all of the text in the input as a String, by using \Z (entire input) as the delimiter. For example, this can be used to read all text in a text file in one line: String content = new Scanner(new File("filename")).useDelimiter("\\Z").next(); System.o...

You can use custom delimiters (regular expressions) with Scanner, with .useDelimiter(","), to determine how the input is read. This works similarly to String.split(...). For example, you can use Scanner to read from a list of comma separated values in a String: Scanner scanner = null; tr...

The JavaScriptSerializer.Deserialize<T>(input) method attempts to deserialize a string of valid JSON into an object of the specified type <T>, using the default mappings natively supported by JavaScriptSerializer. using System.Collections; using System.Web.Script.Serialization; // ....

internal class Sequence{ public string Name; public List<int> Numbers; } // ... string rawJSON = "{\"Name\":\"Fibonacci Sequence\",\"Numbers\":[0, 1, 1, 2, 3, 5, 8, 13]}"; Sequence sequence = JsonConvert.DeserializeObject<Seque...

DOM stands for Document Object Model. It is an object-oriented representation of structured documents like XML and HTML. Setting the textContent property of an Element is one way to output text on a web page. For example, consider the following HTML tag: <p id="paragraph"></p&g...

Introduction All modern web browsers, NodeJs as well as almost every other JavaScript environments support writing messages to a console using a suite of logging methods. The most common of these methods is console.log(). In a browser environment, the console.log() function is predominantly used f...

var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function () { if (xhttp.readyState === XMLHttpRequest.DONE && xhttp.status === 200) { //parse the response in xhttp.responseText; } }; xhttp.open("GET", "ajax_info.txt", true); xhttp.send(...