Tutorial by Examples: e

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 cannot have a public constructor; however, private constructors are acceptable (constructors for enums are package-private by default): public enum Coin { PENNY(1), NICKEL(5), DIME(10), QUARTER(25); // usual names for US coins // note that the above parentheses and the constructor...

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; ...

String getText(String url) throws IOException { HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection(); //add headers to the connection, or check the status if desired.. // handle error response code it occurs int responseCode = conn.getResponseCod...

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...

Sometimes the same functionality has to be written for different kinds of inputs. At that time, one can use the same method name with a different set of parameters. Each different set of parameters is known as a method signature. As seen per the example, a single method can have multiple signatures....

Needed imports: import javax.sound.sampled.AudioSystem; import javax.sound.sampled.Clip; This code will create a clip and play it continuously once started: Clip clip = AudioSystem.getClip(); clip.open(AudioSystem.getAudioInputStream(new URL(filename))); clip.start(); clip.loop(Clip.LOOP_CO...

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....

The switch statement is Java's multi-way branch statement. It is used to take the place of long if-else if-else chains, and make them more readable. However, unlike if statements, one may not use inequalities; each value must be concretely defined. There are three critical components to the switch...

Paginations in JavaFX use a callback to get the pages used in the animation. Pagination p = new Pagination(); p.setPageFactory(param -> new Button(param.toString())); This creates an infinite list of buttons numbed 0.. since the zero arg constructor creates an infinite pagination. setPageFac...

Pagination p = new Pagination(10); Timeline fiveSecondsWonder = new Timeline(new KeyFrame(Duration.seconds(5), event -> { int pos = (p.getCurrentPageIndex()+1) % p.getPageCount(); p.setCurrentPageIndex(pos); })); fiveSecondsWonder.setCycleCount(Timeline.INDEFINITE); fiveSecondsWon...

ArrayList<String> images = new ArrayList<>(); images.add("some\\cool\\image"); images.add("some\\other\\cool\\image"); images.add("some\\cooler\\image"); Pagination p = new Pagination(3); p.setPageFactory(n -> new ImageView(images.get(n))); Note...

wait() and notify() work in tandem – when one thread calls wait() on an object, that thread will block until another thread calls notify() or notifyAll() on that same object. (See Also: wait()/notify() ) package com.example.examples.object; import java.util.concurrent.atomic.AtomicBoolean; p...

The Collections class offers two standard static methods to sort a list: sort(List<T> list) applicable to lists where T extends Comparable<? super T>, and sort(List<T> list, Comparator<? super T> c) applicable to lists of any type. Applying the former requires amending...

MIDI files can be played by using several classes from the javax.sound.midi package. A Sequencer performs playback of the MIDI file, and many of its methods can be used to set playback controls such as loop count, tempo, track muting, and others. General playback of MIDI data can be done in this wa...

In your build.gradle file of main module(app), define your minimum and target version number. android { //the version of sdk source used to compile your project compileSdkVersion 23 defaultConfig { //the minimum sdk version required by device to run your app minSd...

Colors are usually stored in a resource file named colors.xml in the /res/values/ folder. They are defined by <color> elements: <?xml version="1.0" encoding="utf-8"?> <resources> <color name="colorPrimary">#3F51B5</color> <c...