Tutorial by Examples: f

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...

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 = 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...

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...

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...

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...

Java's Reflection API allows the programmer to perform various checks and operations on class fields, methods and annotations during runtime. However, in order for an annotation to be at all visible at runtime, the RetentionPolicy must be changed to RUNTIME, as demonstrated in the example below: @i...

format() from SimpleDateFormat class helps to convert a Date object into certain format String object by using the supplied pattern string. Date today = new Date(); SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MMM-yy"); //pattern is specified here System.out.println(date...

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 { ...

// Required imports import javax.script.ScriptEngineManager; import javax.script.ScriptEngine; import javax.script.ScriptException; import java.io.FileReader; import java.io.FileNotFoundException; // Obtain an instance of the JavaScript engine ScriptEngineManager manager = new ScriptEngineM...

Static and member methods in Java can be marked as native to indicate that their implementation is to be found in a shared library file. Upon execution of a native method, the JVM looks for a corresponding function in loaded libraries (see Loading native libraries), using a simple name mangling sche...

Calling a Java method from native code is a two-step process : obtain a method pointer with the GetMethodID JNI function, using the method name and descriptor ; call one of the Call*Method functions listed here. Java code /*** com.example.jni.JNIJavaCallback.java ***/ package com.example....

This Activity code will provide basic functionality for including a Google Map using a SupportMapFragment. The Google Maps V2 API includes an all-new way to load maps. Activities now have to implement the OnMapReadyCallBack interface, which comes with a onMapReady() method override that is execute...

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...

You should be careful when comparing floating-point values (float or double) using relational operators: ==, !=, < and so on. These operators give results according to the binary representations of the floating point values. For example: public class CompareTest { public static void main...