Tutorial by Examples: b

Group common operations Docker builds images as a collection of layers. Each layer can only add data, even if this data says that a file has been deleted. Every instruction creates a new layer. For example: RUN apt-get -qq update RUN apt-get -qq install some-package Has a couple of downsides: ...

Let's swap the implementation of methodOne() and methodTwo() in our TestSwizzling class: class TestSwizzling : NSObject { dynamic func methodOne()->Int{ return 1 } } extension TestSwizzling { //In Objective-C you'd perform the swizzling in load(), //but t...

The method compareTo should be used to compare BigDecimals: BigDecimal a = new BigDecimal(5); a.compareTo(new BigDecimal(0)); // a is greater, returns 1 a.compareTo(new BigDecimal(5)); // a is equal, returns 0 a.compareTo(new BigDecimal(10)); // a is less, returns -1 Commonly you shou...

A HAVING clause filters the results of a GROUP BY expression. Note: The following examples are using the Library example database. Examples: Return all authors that wrote more than one book (live example). SELECT a.Id, a.Name, COUNT(*) BooksWritten FROM BooksAuthors ba INNER JOIN Aut...

We can use 1,2,3.. to determine the type of order: SELECT * FROM DEPT ORDER BY CASE DEPARTMENT WHEN 'MARKETING' THEN 1 WHEN 'SALES' THEN 2 WHEN 'RESEARCH' THEN 3 WHEN 'INNOVATION' THEN 4 ELSE 5 END, CITY IDREGIONCITYDEPARTMENTEMPLOYEES_N...

PostgreSQL and SQLite To create a temporary table local to the session: CREATE TEMP TABLE MyTable(...); SQL Server To create a temporary table local to the session: CREATE TABLE #TempPhysical(...); To create a temporary table visible to everyone: CREATE TABLE ##TempPhysicalVisibleToEveryo...

Sometimes when tables are used mostly (or only) for reads, indexing does not help anymore and every little bit counts, one might use selects without LOCK to improve performance. SQL Server SELECT * FROM TableName WITH (nolock) MySQL SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;...

WITH cte AS ( SELECT ProjectID, ROW_NUMBER() OVER (PARTITION BY ProjectID ORDER BY InsertDate DESC) AS rn FROM ProjectNotes ) DELETE FROM cte WHERE rn > 1;

The Kernel#require method will load files only once (several calls to require will result in the code in that file being evaluated only once). It will search your ruby $LOAD_PATH to find the required file if the parameter is not an absolute path. Extensions like .rb, .so, .o or .dll are optional. Re...

This function returns the floating-point remainder of the division of x/y. The returned value has the same sign as x. #include <math.h> /* for fmod() */ #include <stdio.h> /* for printf() */ int main(void) { double x = 10.0; double y = 5.1; double modulus = fmod(x,...

Requirements: Docker can be installed on any Linux with a kernel of at least version 3.10. Docker is supported on the following 64-bit versions of Ubuntu Linux: Ubuntu Xenial 16.04 (LTS) Ubuntu Wily 15.10 Ubuntu Trusty 14.04 (LTS) Ubuntu Precise 12.04 (LTS) Easy Installation Note: Installi...

C99 Type Declaration A structure with at least one member may additionally contain a single array member of unspecified length at the end of the structure. This is called a flexible array member: struct ex1 { size_t foo; int flex[]; }; struct ex2_header { int foo; char...

Binding is the process of assigning an object to an identifier or variable name. Early binding (also known as static binding) is when an object declared in Excel is of a specific object type, such as a Worksheet or Workbook. Late binding occurs when general object associations are made, such as the ...

To clone a specific branch of a repository, type --branch <branch name> before the repository url: git clone --branch <branch name> <url> [directory] To use the shorthand option for --branch, type -b. This command downloads entire repository and checks out <branch name>. ...

Autoboxing can come at a substantial memory overhead. For example: Map<Integer, Integer> square = new HashMap<Integer, Integer>(); for(int i = 256; i < 1024; i++) { square.put(i, i * i); // Autoboxing of large integers } will typically consume substantial amount of memory (...

Swift //Swift let viewController = UIViewController() let navigationController = UINavigationController(rootViewController: viewController) //Objective-C UIViewController *viewController = [[UIViewController alloc] init]; UINavigationController *navigationController = [[UINavigationControlle...

As we know that we should use synchronized keyword to make execution of a method or block exclusive. But few of us may not be aware of one more important aspect of using synchronized and volatile keyword: apart from making a unit of code atomic, it also provides read / write barrier. What is this re...

Go to editor (from tool window) Esc Switching focus to corresponding tool window Windows: Alt + <tool window number> OS X / macOS: Cmd + <tool window number> For example switching focus to the project window Windows: Alt + 1 OS X / macOS: Cmd + 1 Recent files popup Windows: Ctrl...

YAML is a text based format allowing to store structured data in a hierarchy. YAML is designed to be human and machine readable with a minimum of overhead. The YAML specification can be found at yaml.org. There is also a reference card Comments start with # and go till newline, comments must be sep...

If you've got multiple implementations of the same interface, Spring can autowire them all into a collection object. I'm going to use an example using a Validator pattern1 Foo Class: public class Foo { private String name; private String emailAddress; private String errorMessage;...