Tutorial by Examples: re

Sorting lists Prior to Java 8, it was necessary to implement the java.util.Comparator interface with an anonymous (or named) class when sorting a list1: Java SE 1.2 List<Person> people = ... Collections.sort( people, new Comparator<Person>() { public int compare(Pe...

Generics enable classes, interfaces, and methods to take other classes and interfaces as type parameters. This example uses generic class Param to take a single type parameter T, delimited by angle brackets (<>): public class Param<T> { private T value; public T getValue() ...

RelativeLayout is a ViewGroup that displays child views in relative positions. By default, all child views are drawn at the top-left of the layout, so you must define the position of each view using the various layout properties available from RelativeLayout.LayoutParams. The value for each layout...

Resources can be added for a specific product flavor. For this example, assume that we have already defined two product flavors called free and paid. In order to add product flavor-specific resources, we create additional resource folders alongside the main/res folder, which we can then add resourc...

Basic cases int[] numbers1 = new int[3]; // Array for 3 int values, default value is 0 int[] numbers2 = { 1, 2, 3 }; // Array literal of 3 int values int[] numbers3 = new int[] { 1, 2, 3 }; // Array of 3 int values initialized int[][] numbers4 = { { 1, 2...

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...

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...

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"); ...

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...

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...

From the documentation: The exception that is thrown when an application attempts to perform a networking operation on its main thread. This is only thrown for applications targeting the Honeycomb SDK or higher. Applications targeting earlier SDK versions are allowed to do networking on their ma...

If you need to produce a JSON string with a value of null like this: { "name":null } Then you have to use the special constant JSONObject.NULL. Functioning example: jsonObject.put("name", JSONObject.NULL);

Java SE 5 With Java 5 and up, one can use for-each loops, also known as enhanced for-loops: List strings = new ArrayList(); strings.add("This"); strings.add("is"); strings.add("a for-each loop"); for (String string : strings) { System.out.println(string); } For each ...

public class MyActivity extends Activity { private static final String PREFS_FILE = "NameOfYourPrefrenceFile"; // PREFS_MODE defines which apps can access the file private static final int PREFS_MODE = Context.MODE_PRIVATE; // you can use live template "key"...

If you want to take a screenshot from the Android Emulator (2.0), then you just need to press Ctrl + S or you click on the camera icon on the side bar: If you use an older version of the Android Emulator or you want to take a screenshot from a real device, then you need to click on the camera ico...

If you have many tasks to execute, and all these tasks are not dependent of the result of the precedent ones, you can use Multithreading for your computer to do all this tasks at the same time using more processors if your computer can. This can make your program execution faster if you have some bi...

private static final String MY_PREF = "MyPref"; // ... SharedPreferences prefs = ...; // ... SharedPreferences.Editor editor = prefs.edit(); editor.putString(MY_PREF, "value"); editor.remove(MY_PREF); editor.apply(); After the apply(), prefs contains "key&q...

Using BufferedReader: System.out.println("Please type your name and press Enter."); BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); try { String name = reader.readLine(); System.out.println("Hello, " + name + "!"); } catch(I...

The Arrays.asList() method can be used to return a fixed-size List containing the elements of the given array. The resulting List will be of the same parameter type as the base type of the array. String[] stringArray = {"foo", "bar", "baz"}; List<String> stringL...