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Difference between a class and a module
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@Caffeine not really because Ruby modules actually include implementations, whereas interfaces in Java are abstract
– Jorge Israel Peña
Jan 12 '13 at 6:34
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How does one reorder columns in a data frame?
... has four columns like so df[,c(1,2,3,4)].
Note the first comma means keep all the rows, and the 1,2,3,4 refers to the columns.
To change the order as in the above question do df2[,c(1,3,2,4)]
If you want to output this file as a csv, do write.csv(df2, file="somedf.csv")
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Difference between Activity Context and Application Context
...nformation about the current activity that is necessary to complete those calls. If you show the exact error message, might be able to point to what exactly it needs.
But in general, use the activity context unless you have a good reason not to.
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How to make links in a TextView clickable?
...ot
// respond to user input. To make them active, you need to
// call setMovementMethod() on the TextView object.
TextView t2 = (TextView) findViewById(R.id.text2);
t2.setMovementMethod(LinkMovementMethod.getInstance());
I removed most of the attributes on my TextView to match wh...
Add file extension to files with bash
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second one adds an extension on all files, not just extensionless ones
– Jeff
Mar 24 '15 at 15:55
5
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Getting an element from a Set
...as already been added to the Set? For example, when .equals() does not use all of the fields, as the OP specified. A less efficient solution would be to remove the element and re-add it with its values updated.
– KyleM
Feb 19 '13 at 17:48
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Class with single method — best approach?
...lity either before or after the old method, we can create a new class and call the old one inside of it - but that's just gross.
Interface woes
Static methods cannot be defined through interfaces for logic reasons. And since we can't override static methods, static classes are useless when we need ...
Virtual functions and performance - C++
...e a very slight effect on performance, but it's unlikely to affect the overall performance of your application. Better places to look for performance improvements are in algorithms and I/O.
An excellent article that talks about virtual functions (and more) is Member Function Pointers and the Fastes...
How is set() implemented?
...ts in python have O(1) membership-checking. How are they implemented internally to allow this? What sort of data structure does it use? What other implications does that implementation have?
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Initializing multiple variables to the same value in Java
...n, thirdPerson;
firstPerson = secondPerson = thirdPerson = new Person();
All the variables would be pointing to the same instance. Probably what you would need in that case is:
Person firstPerson = new Person();
Person secondPerson = new Person();
Person thirdPerson = new Person();
Or better ye...