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String is immutable. What exactly is the meaning? [duplicate]
...ith the fuss of immutability, let's just take a look into the String class and its functionality a little before coming to any conclusion.
This is how String works:
String str = "knowledge";
This, as usual, creates a string containing "knowledge" and assigns it a reference str. Simple enough? Le...
Label encoding across multiple columns in scikit-learn
...
We don't need a LabelEncoder.
You can convert the columns to categoricals and then get their codes. I used a dictionary comprehension below to apply this process to every column and wrap the result back into a dataframe of the same shape with identical indices a...
Access-control-allow-origin with multiple domains
...Allow-Origin). Rewrite uses underscores "_" instead of dashes "-" (rewrite converts them to dashes)
Explaining the server variable HTTP_ORIGIN :
Similarly, in Rewrite you can grab any Request Header using HTTP_ as the prefix. Same rules with the dashes (use underscores "_" instead of dashes "-").
...
C# nullable string error
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System.String is a reference type and already "nullable".
Nullable<T> and the ? suffix are for value types such as Int32, Double, DateTime, etc.
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Is there a regular expression to detect a valid regular expression?
...n directly. (The (?1) and (?R) constructs.) The recursion would have to be converted to counting balanced groups:
^ # start of string
(?:
(?: [^?+*{}()[\]\\|]+ # literals and ^, $
| \\. # escaped charact...
Combine multiple Collections into a single logical Collection?
...terate over all elements (ideally, read only).
I'm using guava collections and I wonder how I could use guava iterables/iterators to generate a logical view on the internal collections without making temporary copies.
...
Finding child element of parent pure javascript
... parent
2. get the parent nodename by using parent.nodeName.toLowerCase() convert the nodename to lower case e.g DIV will be div
3. for further specific purpose, get an attribute of the parent e.g parent.getAttribute("id"). this will give you id of the parent
4. Then use document.QuerySelectorAll...
What is the convention for word separator in Java package names?
...ins a hyphen, or any other special character not allowed in an identifier, convert it into an underscore.
If any of the resulting package name components are keywords then append underscore to them.
If any of the resulting package name components start with a digit, or any other character that i...
What is the native keyword in Java for?
... actual implementation doesn’t have to use JNI. Certain JRE methods are handled intrinsically by the JVM. In fact, it’s not even mandatory that the implementation is actually native code. It’s just “implemented in a language other than the Java programming language”.
–...
Super-simple example of C# observer/observable with delegates
...re's an example:
using System;
class Observable
{
public event EventHandler SomethingHappened;
public void DoSomething() =>
SomethingHappened?.Invoke(this, EventArgs.Empty);
}
class Observer
{
public void HandleEvent(object sender, EventArgs args)
{
Console.Wri...