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What is an efficient way to implement a singleton pattern in Java? [closed]
...
Use an enum:
public enum Foo {
INSTANCE;
}
Joshua Bloch explained this approach in his Effective Java Reloaded talk at Google I/O 2008: link to video. Also see slides 30-32 of his presentation (effective_java_reloaded.pdf):
The Right Way to...
Split column at delimiter in data frame [duplicate]
...
I added a "x|y" line to avoid ambiguities:
df <- data.frame(ID=11:13, FOO=c('a|b','b|c','x|y'))
foo <- data.frame(do.call('rbind', strsplit(as.character(df$FOO),'|',fixed=TRUE)))
Or, if you want to replace the columns in the existing data.frame:
within(df, FOO<-data.frame(do.call('rbin...
How to import a Python class that is in a directory above?
...e to OP's question.
Python is a modular system
This is why we write import foo to load a module "foo" from the root namespace, instead of writing:
foo = dict(); # please avoid doing this
with open(os.path.join(os.path.dirname(__file__), '../foo.py') as foo_fh: # please avoid doing this
exec(co...
How to force 'cp' to overwrite directory instead of creating another one inside?
...Bash script that will overwrite an existing directory. I have a directory foo/ and I am trying to overwrite bar/ with it. But when I do this:
...
How to iterate through two lists in parallel?
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Python 3
for f, b in zip(foo, bar):
print(f, b)
zip stops when the shorter of foo or bar stops.
In Python 3, zip
returns an iterator of tuples, like itertools.izip in Python2. To get a list
of tuples, use list(zip(foo, bar)). And to zip until...
When should Flask.g be used?
...print('in app context, before first request context')
print('setting g.foo to abc')
g.foo = 'abc'
print('g.foo should be abc, is: {0}'.format(g.foo))
with app.test_request_context():
print('in first request context')
print('g.foo should be abc, is: {0}'.format(g.foo)...
When should std::move be used on a function return value? [duplicate]
...
In the case of return std::move(foo); the move is superfluous because of 12.8/32:
When the criteria for elision of a copy operation are met or would be
met save for the fact that the source object is a function parameter,
and the object to be copied...
Mockito : how to verify method was called on an object created within a method?
...ve the access necessary to do perform the test.
Factory Example:
Given a Foo class written like this:
public class Foo {
private BarFactory barFactory;
public Foo(BarFactory factory) {
this.barFactory = factory;
}
public void foo() {
Bar bar = this.barFactory.createBar();
b...
What is the difference between char * const and const char *?
...ple variables are specified in the same declaration? I believe const int *foo,*bar; would declare both foo and bar to be int const *, but int const *foo, *bar would declare foo to be a int const * and bar to be int *. I think typedef int * intptr; const intptr foo,bar; would declare both variables...
Difference between `set`, `setq`, and `setf` in Common Lisp?
...TF, just the SET function.
What is now written as:
(setf (symbol-value '*foo*) 42)
was written as:
(set (quote *foo*) 42)
which was eventually abbreviavated to SETQ (SET Quoted):
(setq *foo* 42)
Then lexical variables happened, and SETQ came to be used for assignment to them too -- so it w...