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中缀表达式
/** * @ 文件名: `01.中缀表达式` * @ 创建者: ty * @ 时间: 2018/7/20 14:27 * @ 描述: infix * Tom sayHelloTo John */ fun main(args: Array<String>) { val pair = "a" to 1 val tom = Person() tom.sayHelloTo("John") tom sayHelloTo "John"//方法前面添加infix关键字 } class Person { infix fun sayHelloTo(name: String) { "你好$name" } }
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类委托
/** * @ 文件名: `02.类委托` * @ 创建者: ty * @ 时间: 2018/7/20 14:27 * @ 描述: by * 小头爸爸委托大头儿子洗碗 */ fun main(args: Array<String>) { val smallHeadFather = SmallHeadFather() smallHeadFather.wash() } interface WashPower { fun wash() } class SmallHeadFather : WashPower by BigHeadSon() class BigHeadSon : WashPower { override fun wash() { println("大头儿子洗碗") } } -
类委托实现二
/** * @ 文件名: `03.类委托实现二` * @ 创建者: ty * @ 时间: 2018/7/20 14:27 * @ 描述: by */ fun main(args: Array<String>) { val bigHeadSon = BigHeadSon() val smallHeadSon = SmallHeadSon() //val bigHeadFather = BigHeadFather(bigHeadSon) val bigHeadFather = BigHeadFather(smallHeadSon) bigHeadFather.wash() } interface WashPower { fun wash() } class SmallHeadSon : WashPower { override fun wash() { println("小头儿子开始洗碗") } } class BigHeadSon : WashPower { override fun wash() { println("大头儿子开始洗碗") } } class BigHeadFather(var washPower: WashPower) : WashPower by washPower
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类委托功能加强
/** * @ 文件名: `04.类委托功能加强` * @ 创建者: ty * @ 时间: 2018/7/20 14:31 * @ 描述: */ fun main(args: Array<String>) { val smallHeadSon = SmallHeadSon() val bigHeadSon = BigHeadSon() val bigHeadFather = BigHeadFather(smallHeadSon) //val bigHeadFather = BigHeadFather(bigHeadSon) bigHeadFather.wash() } interface WashPower { fun wash() } class SmallHeadSon : WashPower { override fun wash() { println("小头儿子开始洗碗") } } class BigHeadSon : WashPower { override fun wash() { println("大头儿子开始洗碗") } } class BigHeadFather(var washPower: WashPower) : WashPower by washPower { override fun wash() { println("付给洗碗的儿子一块钱") washPower.wash() println("碗洗的不错，下次还找你洗") } }
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属性委托
/** * @ 文件名: `05.属性委托` * @ 创建者: ty * @ 时间: 2018/7/20 14:41 * @ 描述: by * 妈妈帮忙保管压岁钱 */ fun main(args: Array<String>) { val bigHeadSon = BigHeadSon() bigHeadSon.money = 100//收到100块压岁钱 println(bigHeadSon.money)//50 被代保管了一半 } class BigHeadSon { var money: Int by Mother() } class Mother { var moneySon = 0 var moneyMother = 0 operator fun getValue(bigHeadSon: BigHeadSon, property: KProperty<*>): Int { return moneySon } operator fun setValue(bigHeadSon: BigHeadSon, property: KProperty<*>, i: Int) { moneySon = i / 2 moneyMother = i / 2 } }
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惰性加载
/** * @ 文件名: `06.惰性加载` * @ 创建者: ty * @ 时间: 2018/7/20 14:41 * @ 描述: by lazy { } * 字段必须 val 修饰 * 1,by lazy 放到成员变量中，可以单独存在 * 2，by lazy 返回值就是最后一行 * 3, by lazy 是线程安全的 */ fun main(args: Array<String>) { val lazy = Lazy() println(lazy.name) println(lazy.name) println(lazy.name) } class Lazy { val name: String by lazy { println("只初始化一次") "懒加载" } }
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延迟加载
/** * @ 文件名: `07.延迟加载` * @ 创建者: ty * @ 时间: 2018/7/20 15:03 * @ 描述: lateinit * * 1.by lazy 和lateinit 都可以单独使用或者放到成员变量中使用 * 2.by lazy 知道具体值 用的时候再加载,lateinit 不知道具体值 后面再赋值 * 3.by lazy变量必须通过val修饰 lateinit需要通过var修饰 */ fun main(args: Array<String>) { val user = User() println(user.name + user.phone) user.name = "林青霞" user.phone = "110" title = "标题" println(user.name + user.phone) } lateinit var title: String //lateinit var money: Byte //lateinit不支持原始数据类型 class User { lateinit var name: String lateinit var phone: String }
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扩展函数
/** * @ 文件名: `08.扩展函数` * @ 创建者: ty * @ 时间: 2018/7/20 15:10 * @ 描述: String.myIsEmpty() * * 判断字符串是否为空 */ fun main(args: Array<String>) { val str = null //val str = "abc" val isEmpty = str?.myIsEmpty() println(isEmpty) } fun String.myIsEmpty(): Boolean { return this == null || this.isEmpty() }
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kotlin中的object单例
/** * @ 文件名: `09.kotlin中的object单例` * @ 创建者: ty * @ 时间: 2018/7/20 15:48 * @ 描述: object ClassName */ fun main(args: Array<String>) { println(SingleInstance.name) SingleInstance.login("110", "12345") } object SingleInstance { var name: String = "张三"//private static String name; fun login(phone: String, pwd: String) { println("登录成功: $phone + $pwd") } /* 实现单例的关键代码 static { SingleInstance var0 = new SingleInstance(); INSTANCE = var0; name = "张三"; }*/ }
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伴生对象
/** * @ 文件名: `10.伴生对象` * @ 创建者: ty * @ 时间: 2018/7/20 16:21 * @ 描述: companion object { } */ fun main(args: Array<String>) { val person = Person() println(person.age) println(Person.name) } class Person { //非静态属性 var age = 10 companion object { //静态属性 var name = "林志玲" } }
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和Java一样的单例
/** * @ 文件名: `11.和Java一样的单例` * @ 创建者: ty * @ 时间: 2018/7/20 16:35 * @ 描述: */ fun main(args: Array<String>) { println(Utils.instance.isCanLogin("110")) } /** * 1,私有化构造方法：private constructor() * 2,初始化一个私有的静态成员变量：companion object { val instance} * 3,对外提供一个公共的方法返回该对象：by lazy { Utils() } */ class Utils private constructor() { companion object { val instance by lazy { Utils() }//惰性加载，只会加载一次，并且线程安全的 } fun isCanLogin(phone: String): Boolean { return phone.myIsEmpty() && phone.length == 11 } }
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枚举
/** * @ 文件名: `12.枚举` * @ 创建者: ty * @ 时间: 2018/7/20 16:35 * @ 描述: 定义一个枚举类，星期一到星期天 Monday Tuesday Wednesday Thursday Friday Saturday Sunday * 并定义一个方法判断是否是工作日 */ fun main(args: Array<String>) { println(todo(WEEK.TUESDAY)) WEEK.values().forEach { println(it) } } enum class WEEK { MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY } fun todo(week: WEEK): String { return when (week) { in WEEK.MONDAY..WEEK.FRIDAY -> { "工作日" } WEEK.SATURDAY, WEEK.SUNDAY -> { "休息日" } else -> { "其他情况" } } }
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枚举加强
/** * @ 文件名: `13.枚举加强` * @ 创建者: ty * @ 时间: 2018/7/20 16:35 * @ 描述: 定义一个枚举类 初始化三原色 R G B */ fun main(args: Array<String>) { println(COLOR.RED.r) println(COLOR.GREEN.g) println(COLOR.BLUE.b) } enum class COLOR(var r: Int, var g: Int, var b: Int) { RED(255, 0, 0), GREEN(0, 255, 0), BLUE(0, 0, 255) }
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数据类
/** * @ 文件名: `14.数据类` * @ 创建者: ty * @ 时间: 2018/7/20 16:35 * @ 描述: data class 定义一个JavaBean */ fun main(args: Array<String>) { val banner = Banner("title", "http://www.baidu.com", 10011) println(banner.title + banner.url + banner.component3())//第三个元素 id val (title1, url, id) = Banner("title", "http://www.baidu.com", 10011) println(url) } // BaseBean abcd = new Gson().fromJson("json", BaseBean.class); data class Banner( var title: String, var url: String, var id: Int)
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密封类
/** * @ 文件名: `15.密封类` * @ 创建者: ty * @ 时间: 2018/7/20 16:49 * @ 描述: sealed class */ fun main(args: Array<String>) { println(hasRightSon(NedStark.SansaStark())) println(hasRightSon(JohnSnow())) } fun hasRightSon(stark: NedStark):Boolean{ return when (stark) { is NedStark.RobStark -> { true } is NedStark.SansaStark ->{ true } is NedStark.AryaStark->{ true } is NedStark.BrandonStark->{ true } else -> { false } } } //密封类封装的是类型 类型是确定的 sealed class NedStark { class RobStark : NedStark() class SansaStark : NedStark() class AryaStark : NedStark() class BrandonStark : NedStark() } class JohnSnow : NedStark()
