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Difference between Covariance & Contra-variance
...m these objects.
It works because if you're only taking values out of the API, and it's going to return something specific (like string), you can treat that returned value as a more general type (like object).
Contravariance
Canonical examples: IComparer<in T>, Action<in T>
You can c...
Are there any SHA-256 javascript implementations that are generally considered trustworthy?
...
On https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest I found this snippet that uses internal js module:
async function sha256(message) {
// encode as UTF-8
const msgBuffer = new TextEncoder('utf-8').encode(message);
// h...
Sending a notification from a service in Android
...);
notificationManager.notify(0, n);
Best way
Code above needs minimum API level 11 (Android 3.0).
If your minimum API level is lower than 11, you should you use support library's NotificationCompat class like this.
So if your minimum target API level is 4+ (Android 1.6+) use this:
impo...
Excel RTD(Excel Real-Time Data)实时刷新数据技术 - C/C++ - 清泛网 - 专注C/C++及内核技术
...原理，接下来演示如何通过Excel RTD来实现从Google Fiancial API中获取实时行情并刷新数据，Google Financal API，提供了世界各大交易所的实时行情数据，其支持的市场及时效性在其官网上有说明，其使用方法可以参考这篇文章，这里不...
How can I create tests in Android Studio?
...hem to test the parts of your code that just need Java and not the Android APIs. (Sometimes you can make a fake API object to test more things locally. This is called a mocking. A mock Context is an example.)
Instrumented tests. These tests are run on a real device or in the emulator. That makes the...
How to move child element from one parent to another using jQuery [duplicate]
... simple:
$('#parentNode').append($('#childNode'));
According to http://api.jquery.com/append/
You can also select an element on the page and insert it into another:
$('.container').append($('h2'));
If an element selected this way is inserted into a single location
elsewhere in t...
How to clone a case class instance and change just one field in Scala?
...d? I can't find a reference to copy in the "obvious" spots, scala-lang.org/api/current/index.html for instance.
– François Beausoleil
Aug 30 '11 at 20:38
6
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How do you create a dictionary in Java? [closed]
...There's an Abstract Class Dictionary
http://docs.oracle.com/javase/6/docs/api/java/util/Dictionary.html
However this requires implementation.
Java gives us a nice implementation called a Hashtable
http://docs.oracle.com/javase/6/docs/api/java/util/Hashtable.html
...
Android Json and null values
...
"null" != null. The problem is that isNull needs api 9+ and sometimes you want lower apis to work. This answer is well, you can use jsonObject.getString != "null" to.
– sagits
Jul 31 '14 at 19:36
...
Examples of GoF Design Patterns in Java's core libraries
...pattern implementations as possible, found in both the Java SE and Java EE APIs.
Creational patterns
Abstract factory (recognizeable by creational methods returning the factory itself which in turn can be used to create another abstract/interface type)
javax.xml.parsers.DocumentBuilderFactory#newI...