kotlin guide

Lambda with receiver* A method in the body of a lambda function that can invoke a different object without any additional qualifiers, which is not found in Java.* Such lambda is called "Lambda with receiver"Let's start with a normal function as a counter-example:Fun Alphabet (): String { val result = StringBuilder () for (letter in ' A ' ... ') Z ') { result.append (letter) } result.append ("\nnow, I know the alphabet") return result.tostring ()}In the above example, you ca

Kotlin Extension Kotlin can extend the properties and methods of a class and do not need to inherit.An extension is a static behavior that does not have any effect on the extended class code itself. Extension of the class, what a ghost. Anyway, I have never seen Java, the following look at the expansion of the Kotlin bar. I. Extension methods is to add a method.

Kotlin Object expressions and object declarations Kotlin uses object expressions and object declarations to implement an object that creates a class that makes minor changes to a class, and does not need to declare a new subclass. an object expression An object that implements an anonymous inner class through an object expression is used in the parameters of the method: Window.addmouselistener (Object:mous

In Kotlin, we can compose an object into multiple variables: Data class Person (Val name:string= "Kotlin", Val sex:string= "man", Val age:int=1) Fun foo () { var (name, Sex,age) =person ()//Deconstruction Declaration print ("Name= $name sex= $sex age= $age") } This is the deconstruction declaration. A destructor declaration can declare multiple variables at once, and any expression can appear on t

The most basic use of an enumeration class is to implement type-safe enumerations Enum class Direction {North , SOUTH, West, East } Kotlin Each enumerated constant is an object. Enumeration constants are separated by commas. Class Because each enumeration is an instance of an enumeration class, they can be initialized. Enum Class Color (Val rgb:int) { RED (0xff0000), GREEN (0x00ff00), BLUE (0x0000ff) }

Kotlin official website:https://kotlinlang.orgwe can get from GitHub Download . Currently The latest version is 1.1.2-5Https://github.com/JetBrains/kotlin/releases/tag/v1.1.2-5Pull down below and you can seeAfter downloading the extract, add the bin directory inside the path of the system environment variable, you can. Of course, the premise is that the system has built a Java environmentCMD input kotlinc-

Associated Objects analogy Java Do you still remember static statically members in Java? Attributes and methods declared as static idioms are initialized at class loading, parsing, and then their lifecycle is bound to the life cycle of the class. 1. This allows certain variables and methods in a class to be bound to the class, rather than bound to an object, to increase its life cycle. 2. This allows objects of this class to share this variable and method without allocating resources for eac

Annotation definition Annotations Annotation Class Fancy constructor for annotations can take parameters Annotation Class Special (Val why:string) Special ("Example") class Foo {} using Annotations @fancy class Foo { @fancy fun baz (@fancy foo:int): Int { return 1 } } annotations in the main constructor Class Foo @inject Constructor (dependency:mydependency) annotations in property visitors Class Foo { var x:mydependency?=null @inject Set } annotations in

The Magical Wuhan University International Software College, only freshman will attend summer training, now sophomore, examination to 7.9, more than 20 days of the end of the training, and then a few days, but also early to school, poor my summer vacation so no.Then say Kotlin:First look at a class named messageIn this class there is a section of code contained in the companion object, it should be said that the Kotlin class does not support the stati

Kotlin's control flow is the same as in other languages, order, branching, loopingThere are two types of branching, if-else and when (similar to switch in Java).If statement:Operation Result:The case statement in Java not only supports integer values, the latest JVM also supports strings, kotlin when statements are more powerful, switch variables can even be various types such as Double,array, in other words when statements are more powerful than swit