Tutorial by Examples: l

Counting items in a list after filter is applied

// Java: long count = items.stream().filter( item -> item.startsWith("t")).count(); // Kotlin: val count = items.filter { it.startsWith('t') }.size // but better to not filter, but count with a predicate val count = items.count { it.startsWith('t') }

Kotlin • Java 8 Stream Equivalents

How streams work - filter, upper case, then sort a list

// Java: List<String> myList = Arrays.asList("a1", "a2", "b1", "c2", "c1"); myList.stream() .filter(s -> s.startsWith("c")) .map(String::toUpperCase) .sorted() .forEach(System.out::println); // C1 ...

Kotlin • Java 8 Stream Equivalents

Collect example #5 - find people of legal age, output formatted string

// Java: String phrase = persons .stream() .filter(p -> p.age >= 18) .map(p -> p.name) .collect(Collectors.joining(" and ", "In Germany ", " are of legal age.")); System.out.println(phrase); // In Germany Max and Peter a...

Kotlin • Java 8 Stream Equivalents

Collect example #6 - group people by age, print age and names together

// Java: Map<Integer, String> map = persons .stream() .collect(Collectors.toMap( p -> p.age, p -> p.name, (name1, name2) -> name1 + ";" + name2)); System.out.println(map); // {18=Max, 23=Peter;Pamela, ...

Kotlin • Java 8 Stream Equivalents

Collect example #7a - Map names, join together with delimiter

// Java (verbose): Collector<Person, StringJoiner, String> personNameCollector = Collector.of( () -> new StringJoiner(" | "), // supplier (j, p) -> j.add(p.name.toUpperCase()), // accumulator (j1, j2) -> j1.merge(j2), // c...

Kotlin • Java 8 Stream Equivalents

Collect example #7b - Collect with SummarizingInt

// Java: IntSummaryStatistics ageSummary = persons.stream() .collect(Collectors.summarizingInt(p -> p.age)); System.out.println(ageSummary); // IntSummaryStatistics{count=4, sum=76, min=12, average=19.000000, max=23} // Kotlin: // something to hold the stats... da...

Kotlin • Java 8 Stream Equivalents

The Curiously Recurring Template Pattern (CRTP)

CRTP is a powerful, static alternative to virtual functions and traditional inheritance that can be used to give types properties at compile time. It works by having a base class template which takes, as one of its template parameters, the derived class. This permits it to legally perform a static_c...

C++ • Curiously Recurring Template Pattern (CRTP)

External CSS Stylesheet

HTML • Linking Resources

Templating in Class Based Views

You can pass data to a template in a custom variable. In your views.py: from django.views.generic import TemplateView from MyProject.myapp.models import Item class ItemView(TemplateView): template_name = "item.html" def items(self): """ Get all Ite...

Django • Templating

Generating Build Environment with CMake

CMake generates build environments for nearly any compiler or IDE from a single project definition. The following examples will demonstrate how to add a CMake file to the cross-platform "Hello World" C++ code. CMake files are always named "CMakeLists.txt" and should already exis...

C++ • Build Systems

Bold + Italic

Creating ***bold italic*** text is simply a matter of using both **bold** (two asterisks) and *italic* (one asterisk) at the same time, for a total of three asterisks on either side of the text you want to format at once. Creating bold italic text is simply a matter of using both bold (two a...

Markdown • Text Formatting

Building an image from a Dockerfile

Once you have a Dockerfile, you can build an image from it using docker build. The basic form of this command is: docker build -t image-name path If your Dockerfile isn't named Dockerfile, you can use the -f flag to give the name of the Dockerfile to build. docker build -t image-name -f Dockerfi...

Docker • Building images

A simple Dockerfile

FROM node:5 The FROM directive specifies an image to start from. Any valid image reference may be used. WORKDIR /usr/src/app The WORKDIR directive sets the current working directory inside the container, equivalent to running cd inside the container. (Note: RUN cd will not change the current ...

Docker • Building images

Accumulate a list of trap work to run at exit.

Have you ever forgotten to add a trap to clean up a temporary file or do other work at exit? Have you ever set one trap which canceled another? This code makes it easy to add things to be done on exit one item at a time, rather than having one large trap statement somewhere in your code, which may...

Bash • Using "trap" to react to signals and system events

SSL Certs Expiring

This data is collected by the http_unit and scollector. It warns when an alert is going to expire within a certain amount of days, and then goes critical if the cert has passed the expiration date. This follows the recommended default of warn and crit usage in Bosun (warn: something is going to fail...

Bosun • Complete Examples

Header Template

In Bosun templates can reference other templates. For emails notifications, you might have a header template to show things you want in all alerts. Header Template template header { body = ` <style> td, th { padding-right: 10px; } </style> <p s...

Bosun • Complete Examples

Linux Bonding Health

Template Definition template linux.bonding { subject = {{.Last.Status}}: {{.Eval .Alert.Vars.by_host}} bad bond(s) on {{.Group.host}} body = `{{template "header" .}} <h2>Bond Status</h2> <table> <tr><th>Bond</th><th>Slave&...

Bosun • Complete Examples

Low Memory Alert and Template

Templates can be previewed and edited using the Rule Editor tab in Bosun. Use the Jump to links to select the alert you want to edit, then you can use the template button next to macro to switch between the alert an template sections of the configuration. If an alert has multiple instances you can u...

Bosun • Templates: Overview

Embedded Templates and CSS Styles

You can embed another template body into your template via {{template "mysharedtemplate" .}} to reuse shared components. Here is an example that creates a header template that can be reused at the top of all other template bodies. It also uses CSS to stylize the output so that it is easier...

Bosun • Templates: Overview

Generic Template with optional Graphs

It often is faster to use a generic template when first creating a new alert and only specialize the template when you need to display more information. The following template will display a subject with a numerical value, custom formatting, and description string and then a body with up to two grap...

Bosun • Templates: Overview