Tutorial by Examples: ar

It can be useful to load a resource (image, text file, properties, KeyStore, ...) that is packaged inside a JAR. For this purpose, we can use the Class and ClassLoaders. Suppose we have the following project structure : program.jar | \-com \-project | |-file.txt \-Test.class ...

dput() and dget() The easiest way to share a (preferable small) data frame is to use a basic function dput(). It will export an R object in a plain text form. Note: Before making the example data below, make sure you're in an empty folder you can write to. Run getwd() and read ?setwd if you need t...

Local variables (unlike the other variable classes) do not have any prefix local_variable = "local" p local_variable # => local Its scope is dependent on where it has been declared, it can not be used outside the "declaration containers" scope. For example, if a local va...

Class variables have a class wide scope, they can be declared anywhere in the class. A variable will be considered a class variable when prefixed with @@ class Dinosaur @@classification = "Like a Reptile, but like a bird" def self.classification @@classification ...

Global variables have a global scope and hence, can be used everywhere. Their scope is not dependent on where they are defined. A variable will be considered global, when prefixed with a $ sign. $i_am_global = "omg" class Dinosaur def instance_method p "global vars ca...

Instance variables have an object wide scope, they can be declared anywhere in the object, however an instance variable declared on class level, will only be visible in the class object. A variable will be considered an instance variable when prefixed with @. Instance variables are used to set and g...

In Emacs M-x slime will start slime with the default (first) Common Lisp implementation. If there are multiple implementations provided (via variable slime-lisp-implementations), other implementations can be accessed via M-- M-x slime, which will offer the choice of available implementations in mini...

Reflection is useful when it is properly used for right purpose. By using reflection, you can access private variables and re-initialize final variables. Below is the code snippet, which is not recommended. import java.lang.reflect.*; public class ReflectionDemo{ public static void main(St...

Compare two Strings ignoring case: "School".equalsIgnoreCase("school"); // true Don't use text1.toLowerCase().equals(text2.toLowerCase()); Languages have different rules for converting upper and lower case. A 'I' would be converted to 'i' in English. But in Turkish a 'I' ...

An important principle for unit testing is to separate data access from business logic. One efficient technique for this is to define interfaces for data access. Your main class always use a reference to that interface instead of direct reading or writing data. in production code the main class wil...

// Obtain an instance of JavaScript engine ScriptEngineManager manager = new ScriptEngineManager(); ScriptEngine engine = manager.getEngineByName("nashorn"); try { // Set value in the global name space of the engine engine.put("name","Nashorn"); // E...

Let's say you have this line of code: printf("Hello, world!\n"); Now say you want to change the text to "Program exiting." CommandBufferMnemonicci"printf("¦");change in the ".Program exiting.\n<esc>printf("Program exiting.\n");

To check if a required gem is installed, from within your code, you can use the following (using nokogiri as an example): begin found_gem = Gem::Specification.find_by_name('nokogiri') require 'nokogiri' .... <the rest of your code> rescue Gem::LoadError end However, this can ...

This can be easily accomplished by calling Enumerable#to_a on a Range object: (1..10).to_a #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] (a..b) means that it will include all numbers between a and b. To exclude the last number, use a...b a_range = 1...5 a_range.to_a #=> [1, 2, 3, 4] or...

While in insert mode, you can use <C-r> to paste from a register, which is specified by the next keystroke. <C-r>" for example pastes from the unnamed (") register. See :help registers.

This substitute command can use Regular Expressions and will match any instance of foo followed by any( one ) character since the period . in Regular Expressions matches any character, hence the following command will match all instances of foo followed by any character in the current line. :s/foo....

As all threads are running in the same process, all threads have access to the same data. However, concurrent access to shared data should be protected with a lock to avoid synchronization issues. import threading obj = {} obj_lock = threading.Lock() def objify(key, val): print("O...

Code running in different processes do not, by default, share the same data. However, the multiprocessing module contains primitives to help share values across multiple processes. import multiprocessing plain_num = 0 shared_num = multiprocessing.Value('d', 0) lock = multiprocessing.Lock() ...

To rename remote, use command git remote rename The git remote rename command takes two arguments: An existing remote name, for example : origin A new name for the remote, for example : destination Get existing remote name git remote # origin Check existing remote with URL git remote -...

Returns the start index of a the first occurrence of string expression inside another string expression. Parameters list: String to find (up to 8000 chars) String to search (any valid character data type and length, including binary) (Optional) index to start. A number of type int or big int. ...