Tutorial by Examples: di

This will load a JSON file from disk and convert it to the given type. public static <T> T getFile(String fileName, Class<T> type) throws FileNotFoundException { Gson gson = new GsonBuilder() .create(); FileReader json = new FileReader(fileName); return gson....

Sometimes you need to serialize or deserialize some fields in a desired format, for example your backend may use the format "YYYY-MM-dd HH:mm" for dates and you want your POJOS to use the DateTime class in Joda Time. In order to automatically convert these strings into DateTimes object, y...

To enable or disable a BroadcastReceiver, we need to get a reference to the PackageManager and we need a ComponentName object containing the class of the receiver we want to enable/disable: ComponentName componentName = new ComponentName(context, MyBroadcastReceiver.class); PackageManager packageM...

Extension Method can work on null references, but you can use ?. to null-check anyway. public class Person { public string Name {get; set;} } public static class PersonExtensions { public static int GetNameLength(this Person person) { return person == null ? -1 : pers...

namespace CodeContractsDemo { using System; using System.Collections.Generic; using System.Diagnostics.Contracts; public class PaymentProcessor { private List<Payment> _payments = new List<Payment>(); public void Add(Payment payment) ...

public double GetPaymentsTotal(string name) { Contract.Ensures(Contract.Result<double>() >= 0); double total = 0.0; foreach (var payment in this._payments) { if (string.Equals(payment.Name, name)) { total += payment.Amount; } } ...

Displaying all the logs from the default buffer on the Command Line can be accomplished by: adb logcat This command will show you all the logs from the device's main buffer. Notice that if you use it for the first time, you'll get a lot of information, an enormous stream of data. So you may want...

This error happens if a unknown object is used. Variables Not compiling: #include <iostream> int main(int argc, char *argv[]) { { int i = 2; } std::cout << i << std::endl; // i is not in the scope of the main function return 0; } Fix: #i...

The compiler can't find a file (a source file uses #include "someFile.hpp"). qmake: INCLUDEPATH += dir/Of/File cmake: include_directories(dir/Of/File) g++ call: g++ -o main main.cpp -Idir/Of/File

F# uses the type keyword to create different kind of types. Type aliases Discriminated union types Record types Interface types Class types Struct types Examples with equivalent C# code where possible: // Equivalent C#: // using IntAliasType = System.Int32; type IntAliasType = int // ...

eof returns true only after reading the end of file. It does NOT indicate that the next read will be the end of stream. while (!f.eof()) { // Everything is OK f >> buffer; // What if *only* now the eof / fail bit is set? /* Use `buffer` */ } You could correctly write: ...

Although this works only for WebKit based browsers, this is helpful: /* ----------- Non-Retina Screens ----------- */ @media screen and (min-width: 1200px) and (max-width: 1600px) and (-webkit-min-device-pixel-ratio: 1) { } /* ----------- Retina Screens ----------- */ @media scre...

When an object is exposed to the template context, its arguments-less methods are available. This is useful when these functions are "getters". But it can be hazardeous if these methods alter some data or have some side effects. Eventhough you likely trust the template writer, he may not b...

$> pwd /home/myUserHome $> cd .. $> pwd /home will print the current path to the console.

When working with large files, you can use the System.IO.File.ReadLines method to read all lines from a file into an IEnumerable<string>. This is similar to System.IO.File.ReadAllLines, except that it doesn't load the whole file into memory at once, making it more efficient when working with l...

Another straightforward way to go is to create a dictionary of functions: switch = { 1: lambda: 'one', 2: lambda: 'two', 42: lambda: 'the answer of life the universe and everything', } then you add a default function: def default_case(): raise Exception('No case found!') ...

SQL has various join types to specify whether (non-)matching rows are included in the result: INNER JOIN, LEFT OUTER JOIN, RIGHT OUTER JOIN, and FULL OUTER JOIN (the INNER and OUTER keywords are optional). The figure below underlines the differences between these types of joins: the blue area repres...

With the ViewMatchers you can find view in the current view hierarchy. To find a view, use the onView() method with a view matcher which selects the correct view. The onView() methods return an object of type ViewInteraction. For example, finding a view by its R.id is as simple as: onView(withId(...

Inherits Specifies the base (or parent) class Public Class Person End Class Public Class Customer Inherits Person End Class 'One line notation Public Class Student : Inherits Person End Class Possible objects: Dim p As New Person Dim c As New Customer Dim s As New Student ...

Overridable Allows a property or method in a class to be overridden in a derived class. Public Class Person Public Overridable Sub DoSomething() Console.WriteLine("Person") End Sub End Class Overrides Overrides an Overridable property or method defined in the base...