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Difference in System. exit(0) , System.exit(-1), System.exit(1 ) in Java
I'd like to know the difference between the following in Java
11 Answers
11
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Java Generics (Wildcards)
...ces a restriction on the type by saying that it either has to extend a specific type (<? extends T> is known as an upper bound), or has to be an ancestor of a specific type (<? super T> is known as a lower bound).
The Java Tutorials have some pretty good explanations of generics in the ...
Escape regex special characters in a Python string
...ring)
Return string with all non-alphanumerics backslashed; this is useful if you want to match an arbitrary literal string that may have regular expression metacharacters in it.
As of Python 3.7 re.escape() was changed to escape only characters which are meaningful to regex operations.
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Difference between jQuery’s .hide() and setting CSS to display: none
... is quicker than writing out .css("display", "none") , but what’s the difference and what are both of them actually doing to the HTML element?
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mysql :: insert into table, data from another table?
I was wondering if there is a way to do this purely in sql:
5 Answers
5
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What is Data Transfer Object?
...DTOs can be to encapsulate parameters for method calls. This can be useful if a method takes more than 4 or 5 parameters.
When using the DTO pattern, you would also make use of DTO assemblers. The assemblers are used to create DTOs from Domain Objects, and vice versa.
The conversion from Domain Ob...
Remove all special characters, punctuation and spaces from string
...ial $#! characters spaces 888323"
>>> ''.join(e for e in string if e.isalnum())
'Specialcharactersspaces888323'
You can use str.isalnum:
S.isalnum() -> bool
Return True if all characters in S are alphanumeric
and there is at least one character in S, False otherwise.
If you ins...
C/C++ macro string concatenation
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If they're both strings you can just do:
#define STR3 STR1 STR2
The preprocessor automatically concatenates adjacent strings.
EDIT:
As noted below, it's not the preprocessor but the compiler that does the concatenation.
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Uniq by object attribute in Ruby
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The hash method is better if you want to group by say album_id while (say) summing up num_plays.
– thekingoftruth
Sep 13 '13 at 22:59
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Staging Deleted files
...the index to match the current state of the directory as a whole (e.g. specifying dir will record not just a file dir/file1 modified in the working tree, a file dir/file2 added to the working tree, but also a file dir/file3 removed from the working tree. Note that older versions of Git used to ignor...