Tutorial by Examples: l

Examples of using Default Methods introduced in Java 8 in Map interface Using getOrDefault Returns the value mapped to the key, or if the key is not present, returns the default value Map<Integer, String> map = new HashMap<>(); map.put(1, "First element"); map.get(1); ...

Map<Integer, String> map = new HashMap<>(); map.put(1, "First element."); map.put(2, "Second element."); map.put(3, "Third element."); map.clear(); System.out.println(map.size()); // => 0

Consider the following JSON string: { "title": "test", "content": "Hello World!!!", "year": 2016, "names" : [ "Hannah", "David", "Steve" ] } This JSON object can...

Create the JSONObject using the empty constructor and add fields using the put() method, which is overloaded so that it can be used with different types: try { // Create a new instance of a JSONObject final JSONObject object = new JSONObject(); // With put you can add a name/va...

Android logs can be filtered directly from the UI. Using this code public class MainActivity extends AppCompatActivity { private final static String TAG1 = MainActivity.class.getSimpleName(); private final static String TAG2 = MainActivity.class.getCanonicalName(); @Override p...

Custom filters can be set and save from the UI. In the AndroidMonitor tab, click on the right dropdown (must contains Show only selected application or No filters) and select Edit filter configuration. Enter the filter you want And use it (you can selected it from the same dropdown) Important...

First example reimplemented in Kotlin and using RxJava for cleaner interaction. import android.view.LayoutInflater import android.view.View import android.view.ViewGroup import android.support.v7.widget.RecyclerView import rx.subjects.PublishSubject public class SampleAdapter(private val ite...

Two methods in java.util.Collection create an array from a collection: Object[] toArray() <T> T[] toArray(T[] a) Object[] toArray() can be used as follows: Java SE 5 Set<String> set = new HashSet<String>(); set.add("red"); set.add("blue"); ...

Methods can also have generic type parameters. public class Example { // The type parameter T is scoped to the method // and is independent of type parameters of other methods. public <T> List<T> makeList(T t1, T t2) { List<T> result = new ArrayList<T&...

When we create a button in layout, we can use the android:onClick attribute to reference a method in code to handle clicks. Button <Button android:width="120dp" android:height="wrap_content" android:text="Click me" android:onClick="handleCl...

Java 7 introduced the very useful Files class Java SE 7 import java.nio.file.Files; import java.nio.file.Paths; import java.nio.file.Path; Path path = Paths.get("path/to/file"); try { byte[] data = Files.readAllBytes(path); } catch(IOException e) { e.printStackTrace();...

When we create any View in layout, we can use the android:onClick attribute to reference a method in the associated activity or fragment to handle the click events. XML Layout <Button android:id="@+id/button" ... // onClick should reference the method in your activity or fra...

Strings can be internationalised by defining a different strings.xml for each language you support. You add a new language by creating a new values directory with the ISO language code as a suffix. For example, when adding a German set your structure might look like follows: When the system look...

Gradle (Module:app) Configuration android { .... dataBinding { enabled = true } } Data model public class Item { public String name; public String description; public Item(String name, String description) { this.name = name; this.descr...

Data model public class Item { private String name; public String getName() { return name; } } Layout XML You must import referenced classes, just as you would in Java. <?xml version="1.0" encoding="utf-8"?> <layout xmlns:android="h...

/** * Interface with default method */ public interface Printable { default void printString() { System.out.println( "default implementation" ); } } /** * Class which falls back to default implementation of {@link #printString()} */ public class WithDefault...

You can as well access other interface methods from within your default method. public interface Summable { int getA(); int getB(); default int calculateSum() { return getA() + getB(); } } public class Sum implements Summable { @Override public int get...

class TrivialClass {} A class consists at a minimum of the class keyword, a name, and a body, which might be empty. You instantiate a class with the new operator. TrivialClass tc = new TrivialClass();

package com.example; import android.os.Bundle; import android.support.annotation.Nullable; import android.util.Log; import android.view.View; import android.view.ViewTreeObserver; public class ExampleActivity extends Activity { @Override protected void onCreate(@Nullable final ...

// Compile a Uri with the 'mailto' schema Intent emailIntent = new Intent(Intent.ACTION_SENDTO, Uri.fromParts( "mailto","[email protected]", null)); // Subject emailIntent.putExtra(Intent.EXTRA_SUBJECT, "Hello World!"); // Body of email emailIntent.putEx...