Tutorial by Examples: u

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); ...

Under most circumstances, it is simpler from a code-design standpoint to use existing generic Exception classes when throwing exceptions. This is especially true if you only need the exception to carry a simple error message. In that case, RuntimeException is usually preferred, since it is not a che...

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...

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...

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...

/** * 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...

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 ...

In Android Activities and Services, most callbacks are run on the main thread. This makes it simple to update the UI, but running processor- or I/O-heavy tasks on the main thread can cause your UI to pause and become unresponsive (official documentation on what then happens). You can remedy this by...

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);

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"...

Android Studio is the Android development IDE that is officially supported and recommended by Google. Android Studio comes bundled with the Android SDK Manager, which is a tool to download the Android SDK components required to start developing apps. Installing Android Studio and Android SDK tools:...

It is helpful to filter the logcat output because there are many messages which are not of interest. To filter the output, open the "Android Monitor" and click on the drop down on the top-right and select Edit Filter Configuration Now you can add custom filters to show messages which ar...

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...

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...

It is possible to define an array with more than one dimension. Instead of being accessed by providing a single index, a multidimensional array is accessed by specifying an index for each dimension. The declaration of multidimensional array can be done by adding [] for each dimension to a regular a...

All Swing-related operations happen on a dedicated thread (the EDT - Event Dispatch Thread). If this thread gets blocked, the UI becomes non-responsive. Therefore, if you want to delay an operation you cannot use Thread.sleep. Use a javax.swing.Timer instead. For example the following Timer will re...

Updating the state of a Swing component must happen on the Event Dispatch Thread (the EDT). The javax.swing.Timer triggers its ActionListener on the EDT, making it a good choice to perform Swing operations. The following example updates the text of a JLabel each two seconds: //Use a timer to updat...

In the ActionListener attached to a javax.swing.Timer, you can keep track of the number of times the Timer executed the ActionListener. Once the required number of times is reached, you can use the Timer#stop() method to stop the Timer. Timer timer = new Timer( delay, new ActionListener() { priv...