大约有 16,000 项符合查询结果（耗时：0.0791秒） [XML]
Vim: Replacing a line with another one yanked before
At least once per day i have the following situation:
16 Answers
16
...
What is an initialization block?
We can put code in a constructor or a method or an initialization block. What is the use of initialization block? Is it necessary that every java program must have it?
...
Null coalescing in powershell
... you can use the standard Powershell if statements as an expression:
variable = if (condition) { expr1 } else { expr2 }
So to the replacements for your first C# expression of:
var s = myval ?? "new value";
becomes one of the following (depending on preference):
$s = if ($myval -eq $null) { "n...
XPath to select multiple tags
...
One correct answer is:
/a/b/*[self::c or self::d or self::e]
Do note that this
a/b/*[local-name()='c' or local-name()='d' or local-name()='e']
is both too-long and incorrect. This XPath expression will select nodes like:
OhMy:c
NotWanted:d
Qu...
When NOT to call super() method when overriding?
...ustom class, I extend its native class. Then when I want to override the base method, I always call super() method, just like I always do in onCreate , onStop , etc.
...
Combine two or more columns in a dataframe into a new column with a new name
...
Use paste.
df$x <- paste(df$n,df$s)
df
# n s b x
# 1 2 aa TRUE 2 aa
# 2 3 bb FALSE 3 bb
# 3 5 cc TRUE 5 cc
share
|
improve this answer
|
f...
Adding a column to a data.frame
I have the data.frame below. I want to add a column that classifies my data according to column 1 ( h_no ) in that way that the first series of h_no 1,2,3,4 is class 1, the second series of h_no (1 to 7) is class 2 etc. such as indicated in the last column.
...
Why does PHP 5.2+ disallow abstract static class methods?
After enabling strict warnings in PHP 5.2, I saw a load of strict standards warnings from a project that was originally written without strict warnings:
...
Call a function from another file?
...te from file import function, and then call the function using function(a, b). The reason why this may not work, is because file is one of Python's core modules, so I suggest you change the name of your file.
Note that if you're trying to import functions from a.py to a file called b.py, you will n...
assign multiple variables to the same value in Javascript
I have initialized several variables in the global scope in a JavaScript file:
5 Answers
...