Conventions used

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "Demonstrations of null and non-null types."

A block of code is set as follows:

data class Language(val name: String)

fun main(args: Array<String>) {
  val language = Language("Kotlin")
  println(language.name)
}

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

fun main(args: Array<String>) {
    var language: String = "Kotlin"
    language = null // Error: Null can not be a value of a non-null type String
}

Any command-line input or output is written as follows:

$ mkdir css
$ cd css

Bold: Indicates a new term, an important word, or words that you see on screen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "Next, under the Client section, select Jetty HttpClient Engine and then click on Next."

Warnings or important notes appear like this.

Tips and tricks appear like this.