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Once the SDK installed, you can open the AVD Manager from the command line using android avd. You can also access AVD Manager from Android studio using Tools > Android > AVD Manager or by clicking on the AVD Manager icon in the toolbar which is the second in the screenshot below.

The AppCompat support library provides themes to build apps with the Material Design specification. A theme with a parent of Theme.AppCompat is also required for an Activity to extend AppCompatActivity. The first step is to customize your theme’s color palette to automatically colorize your app. I...

A Toolbar is a generalization of ActionBar for use within application layouts. While an ActionBar is traditionally part of an Activity's opaque window decor controlled by the framework, a Toolbar may be placed at any arbitrary level of nesting within a view hierarchy. It can be added by performing t...

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...

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...

For basic prototypes or basic command-line behavior, the following loop comes in handy. public class ExampleCli { private static final String CLI_LINE = "example-cli>"; //console like string private static final String CMD_QUIT = "quit"; //string for exit...

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...

public interface MyInterface { public void foo(); int bar(); public String TEXT = "Hello"; int ANSWER = 42; public class X { } class Y { } } Interface members always have public visibility, even if the public keyword is omitted. So both foo...

Following snippet shows an example of passing a method group (as opposed to a lambda) when a delegate is expected. Overload resolution will now resolve this instead of raising an ambiguous overload error due to the ability of C# 6 to check the return type of the method that was passed. using System...

It is possible to generate a Stream that does not end. Calling a terminal method on an infinite Stream causes the Stream to enter an infinite loop. The limit method of a Stream can be used to limit the number of terms of the Stream that Java processes. This example generates a Stream of all natural...

The ArrayIndexOutOfBoundsException is thrown when a non-existing index of an array is being accessed. Arrays are zero-based indexed, so the index of the first element is 0 and the index of the last element is the array capacity minus 1 (i.e. array.length - 1). Therefore, any request for an array e...

The String type provides two methods for converting strings between upper case and lower case: toUpperCase to convert all characters to upper case toLowerCase to convert all characters to lower case These methods both return the converted strings as new String instances: the original String o...

private visibility allows a variable to only be accessed by its class. They are often used in conjunction with public getters and setters. class SomeClass { private int variable; public int getVariable() { return variable; } public void setVariable(int variable) { ...

With no modifier, the default is package visibility. From the Java Documentation, "[package visibility] indicates whether classes in the same package as the class (regardless of their parentage) have access to the member." In this example from javax.swing, package javax.swing; public abs...

If you need to extract a part of string from the input string, we can use capture groups of regex. For this example, we'll start with a simple phone number regex: \d{3}-\d{3}-\d{4} If parentheses are added to the regex, each set of parentheses is considered a capturing group. In this case, we a...

To check whether a particular String a is being contained in a String b or not, we can use the method String.contains() with the following syntax: b.contains(a); // Return true if a is contained in b, false otherwise The String.contains() method can be used to verify if a CharSequence can be fou...

In order to get the length of a String object, call the length() method on it. The length is equal to the number of UTF-16 code units (chars) in the string. String str = "Hello, World!"; System.out.println(str.length()); // Prints out 13 Live Demo on Ideone A char in a String is UTF...