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Can we write our own iterator in Java?
If I have a list containing [alice, bob, abigail, charlie] and I want to write an iterator such that it iterates over elements that begin with 'a', can I write my own ? How can I do that ?
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How important is the order of columns in indexes?
... Also keep in mind, suppose your Index is like the picture above, and your query filters on column1 and column2, but column2 is more unique and what you really want to filter on is actually column2, then its more beneficial to just have a index where column 2 is first. This may seem counte...
When do you use varargs in Java?
...at("This is an integer: %d", myInt);
String.format("This is an integer: %d and a string: %s", myInt, myString);
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Clean ways to write multiple 'for' loops
.../ ...
}
(or just:
for ( auto& elem: m ) {
}
if you have C++11.)
And if you need the three indexes during such iterations, it's
possible to create an iterator which exposes them:
class Matrix3D
{
// ...
class iterator : private std::vector<int>::iterator
{
Matri...
Get current time in seconds since the Epoch on Linux, Bash
...e , but in seconds since 1970 instead of the current date, hours, minutes, and seconds.
7 Answers
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Summarizing multiple columns with dplyr? [duplicate]
... a bit with the dplyr-syntax. I have a data frame with different variables and one grouping variable. Now I want to calculate the mean for each column within each group, using dplyr in R.
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Method call if not null in C#
...ke();
or:
obj?.SomeMethod();
The ?. is the null-propagating operator, and will cause the .Invoke() to be short-circuited when the operand is null. The operand is only accessed once, so there is no risk of the "value changes between check and invoke" problem.
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Prior to C# 6, no: there is no...
How to Deserialize XML document
...entAttribute labels to XmlElement because in the xml the StockNumber, Make and Model values are elements, not attributes. Also I removed the reader.ReadToEnd(); (that function reads the whole stream and returns a string, so the Deserialize() function couldn't use the reader anymore...the position w...
How do I replace a character at a particular index in JavaScript?
I have a string, let's say Hello world and I need to replace the char at index 3. How can I replace a char by specifying a index?
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Correct way to check if a type is Nullable [duplicate]
...sting disagreement between the specification (your link in the first line) and the actual behavior. For your propertyType object from the last line is a counter-example. What I mean is that Nullable.GetUnderlyingType(propertyType) does not return null (it returns your T) although propertyType is an ...