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Immutable vs Unmodifiable collection
...ects themselves may still be mutable - creating an immutable collection of StringBuilder doesn't somehow "freeze" those objects.
Basically, the difference is about whether other code may be able to change the collection behind your back.
...
How to track down a “double free or corruption” error
...debug it.
#include<stdio.h>
#include<stdlib.h>
int main()
{
char *x = malloc(100);
free(x);
free(x);
return 0;
}
[sand@PS-CNTOS-64-S11 testbox]$ vim t1.c
[sand@PS-CNTOS-64-S11 testbox]$ cc -g t1.c -o t1
[sand@PS-CNTOS-64-S11 testbox]$ ./t1
*** glibc detected *** ./t1: double free ...
Should private helper methods be static if they can be static
...ate static void doSomethingStatic(int arg) { }
public static void main(String[] args) {
// do it twice both ways
doSomethingStatic(0);
doSomethingStatic(0);
TestBytecodeSize t = new TestBytecodeSize();
t.doSomething(0);
t.doSomething(0);
}
}
...
How to “pretty” format JSON output in Ruby on Rails
...nController::Renderers.add :json do |json, options|
unless json.kind_of?(String)
json = json.as_json(options) if json.respond_to?(:as_json)
json = JSON.pretty_generate(json, options)
end
if options[:callback].present?
self.content_type ||= Mime::JS
"#{options[:callback]}(#{jso...
How to check sbt version?
...t project to jacek (in build file:/Users/jacek/)
[info] Setting: java.lang.String = 0.13.1
[info] Description:
[info] Provides the version of sbt. This setting should be not be modified.
[info] Provided by:
[info] */*:sbtVersion
[info] Defined at:
[info] (sbt.Defaults) Defaults.scala:68
[info] D...
jQuery .data() does not work, but .attr() does
...ia .data() will return an Object while retrieval via .attr() will return a string. See jsfiddle example.
Since .data() does extra processing jQuery stores the results of attribute evaluation in $.cache - after all, once a data attribute has been evaluated it would be wasteful to re-evaluate on ever...
Android Studio with Google Play Services
...he sdk manager and download and install the following files located under "extras": Android support repository, Google play services, Google repository.
Restart android studio and open the build gradle file. You must modify your build.gradle file to look like this under dependencies:
dependencies ...
Count, size, length…too many choices in Ruby?
...
In most cases (e.g. Array or String) size is an alias for length.
count normally comes from Enumerable and can take an optional predicate block. Thus enumerable.count {cond} is [roughly] (enumerable.select {cond}).length -- it can of course bypass the i...
Javascript Shorthand for getElementById
...
To save an extra character you could pollute the String prototype like this:
pollutePrototype(String, '绎', {
configurable: false, // others must fail
get: function() {
return document.getElementById(this);
},
set: function(element) {
eleme...
Which, if any, C++ compilers do tail-recursion optimization?
...t for program correctness.
#include <stdio.h>
static int atoi(const char *str, int n)
{
if (str == 0 || *str == 0)
return n;
return atoi(str+1, n*10 + *str-'0');
}
int main(int argc, char **argv)
{
for (int i = 1; i != argc; ++i)
printf("%s -> %d\n", argv[i], at...