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How do I use the new computeIfAbsent function?

...onacci(0) memo.put(1,1L); //fibonacci(1) } And for the inductive step all we have to do is redefine our Fibonacci function as follows: public static long fibonacci(int x) { return memo.computeIfAbsent(x, n -> fibonacci(n-2) + fibonacci(n-1)); } As you can see, the method computeIfAbsen...
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Serialize an object to string

...(T) in XmlSerializer constructor: if you use the first one the code covers all possible subclasses of T (which are valid for the method), while using the latter one will fail when passing a type derived from T.    Here is a link with some example code that motivate this statement, with XmlSerializ...
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Subclassing a Java Builder class

... You can solve it using generics. I think this is called the "Curiously recurring generic patterns" Make the return type of the base class builder methods a generic argument. public class NutritionFacts { private final int calories; public static class Builder<...
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Checking for a null int value from a Java ResultSet

... declaration. In which case your test is completely redundant. If you actually want to do something different if the field value is NULL, I suggest: int iVal = 0; ResultSet rs = magicallyAppearingStmt.executeQuery(query); if (rs.next()) { iVal = rs.getInt("ID_PARENT"); if (rs.wasNull()) { ...
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How to write a:hover in inline CSS?

...defining the selection criteria). Response to the OP's comments: See Totally Pwn CSS with Javascript for a good script on adding CSS rules dynamically. Also see Change style sheet for some of the theory on the subject. Also, don't forget, you can add links to external stylesheets if that's an op...
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Why do people use __(double underscore) so much in C++

...specific, and are slightly more detailed than some others have suggested. All identifiers that contain a double underscore or start with an underscore followed by an uppercase letter are reserved for the use of the implementation at all scopes, i.e. they might be used for macros. In addition, all ...
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What is the difference between IQueryable and IEnumerable?

... First of all, IQueryable<T> extends the IEnumerable<T> interface, so anything you can do with a "plain" IEnumerable<T>, you can also do with an IQueryable<T>. IEnumerable<T> just has a GetEnumerator() m...
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sqlalchemy: how to join several tables by one query?

...rmissions.document, ).filter( User.email == 'someemail', ).all() share | improve this answer | follow | ...
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How to remove all whitespace from a string?

...\r\v\fy \t\n\r\v\f" ## [4] NA The base R approach: gsub gsub replaces all instances of a string (fixed = TRUE) or regular expression (fixed = FALSE, the default) with another string. To remove all spaces, use: gsub(" ", "", x, fixed = TRUE) ## [1] "xy" "←→" ...
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Date format Mapping to JSON Jackson

... Tried all these solutions but was not able to store a Date variable of my POJO into a Map key value, also as Date. I want this to then instantiate a BasicDbObject (MongoDB API) from the Map, and consequently store the variable in ...