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What does the question mark in Java generics' type parameter mean?
...technical terms, ? extends HasWord is a bounded wildcard, covered in Item 31 of Effective Java 3rd Edition, starting on page 139. The same chapter from the 2nd Edition is available online as a PDF; the part on bounded wildcards is Item 28 starting on page 134.
Update: PDF link was updated since Or...
C++ Modules - why were they removed from C++0x? Will they be back later on?
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answered Aug 29 '10 at 19:07
James McNellisJames McNellis
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CSS center display inline block?
...lay: inline-block to be both horizontally and vertically centered within a 100% width parent.
I used Flexbox's justify-content and align-items properties, which respectively allow you to center elements horizontally and vertically. By setting both to center on the parent, the child element (or eve...
find() with nil when there are no records
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173
Yes, just do:
Challenge.find_by_id(10)
For Rails 4 and 5:
Challenge.find_by(id: 10)
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What does the keyword Set actually do in VBA?
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edited Feb 9 '17 at 20:42
TylerH
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a...
Introducing FOREIGN KEY constraint may cause cycles or multiple cascade paths - why?
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从估值5千万到一无所有 90后的他感觉梦境一场 - 资讯 - 清泛网 - 专注C/C++...
...业，当时只有5个人，做一个宠物交易和服务的项目。
2015年1月，20出头的夏军迎来第一波人生高峰，他创办的爱狗团获得了天使轮投资。按照投资协议，对方出资1000万元，分5次给清，占股20%，项目估值5000万元。当时投资人已...
How to Detect if I'm Compiling Code with a particular Visual Studio version?
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_MSC_VER and possibly _MSC_FULL_VER is what you need. You can also examine visualc.hpp in any r...
How to vertical align an inline-block in a line of text?
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168
code {
background: black;
color: white;
display: inline-block;
vertica...
sqlite alter table add MULTIPLE columns in a single statement
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No, you have to add them one at a time. See the syntax diagram at the top of SQLite's ALTER TAB...