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Should I use string.isEmpty() or “”.equals(string)?
...always wondering why others use this so often, but didn't take null values into account. Great :-)
– Peter Wippermann
Dec 2 '10 at 10:51
10
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Selecting with complex criteria from pandas.DataFrame
...tup:
>>> import pandas as pd
>>> from random import randint
>>> df = pd.DataFrame({'A': [randint(1, 9) for x in range(10)],
'B': [randint(1, 9)*10 for x in range(10)],
'C': [randint(1, 9)*100 for x in range(10)]})
>>> df
A...
Ship an application with a database
...ase in the assets folder with the new database, saving the old database in internal storage under another name, copying the new database from the assets folder into internal storage, transferring all of the data from the old database (that was renamed earlier) into the new database and finally delet...
How to determine if binary tree is balanced?
... abs(Height(tree.left) - Height(tree.right)) <= 1)
Translating that into the programming language of your choice should be trivial.
Bonus exercise: this naive code sketch traverses the tree far too many times when computing the heights. Can you make it more efficient?
Super bonus exercise: ...
Task not serializable: java.io.NotSerializableException when calling function outside closure only o
...
RDDs extend the Serialisable interface, so this is not what's causing your task to fail. Now this doesn't mean that you can serialise an RDD with Spark and avoid NotSerializableException
Spark is a distributed computing engine and its main abstraction i...
ORDER BY the IN value list
...
You can do it quite easily with (introduced in PostgreSQL 8.2) VALUES (), ().
Syntax will be like this:
select c.*
from comments c
join (
values
(1,1),
(3,2),
(2,3),
(4,4)
) as x (id, ordering) on c.id = x.id
order by x.ordering
...
Difference between shadowing and overriding in C#?
...
Well inheritance...
suppose you have this classes:
class A {
public int Foo(){ return 5;}
public virtual int Bar(){return 5;}
}
class B : A{
public new int Foo() { return 1;} //shadow
public override int Bar() {return 1;} //override
}
then when you call this:
A clA = new A();
...
How to implement one-to-one, one-to-many and many-to-many relationships while designing tables?
... # "link back" if you need
You must also put a unique constraint on the foreign key column (addess.student_id) to prevent multiple rows in the child table (address) from relating to the same row in the referenced table (student).
One-to-many: Use a foreign key on the many side of the ...
What is the exact problem with multiple inheritance?
...people asking all the time whether multiple inheritance should be included into the next version of C# or Java. C++ folks, who are fortunate enough to have this ability, say that this is like giving someone a rope to eventually hang themselves.
...
How to get the filename without the extension in Java?
...brary solution above. It works, but looking at the code (without having to interpret the REGEX) isn't obvious what it does.
– Gustavo Litovsky
Nov 28 '12 at 21:12
5
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