Android第⼀⾏代码（第三版）-Kotlin语法
参考：第⼀⾏代码
在Project视图下，我的项⽬名称是Myapp
到MyApp->app->src->main->java-&app路径下，右键点击app，创建⼀个kotlin⽂件，名字为LearnKotlin
learnKotlin.kt⽂件
app
import java.lang.NumberFormatException
import kotlin.math.max
菱角剥壳机import kotlin.math.min
fun main(){
println("hello world")
var a: Int =10
val i: Int =10
val l: Long =1000
val s: Short =100
val b: Byte =1
val f: Float =10.1F
val d: Double =10.02
val c: Char ='a'
val bo: Boolean =true
println("b= "+ b)
println("s = "+ s)
println("i = "+ i)
木酢液println("l = "+ l)
println("f = "+ f)
println("d = "+ d)
println("bo = "+ bo)
println("测试基本类型运算和var val"+" \n")
println("a = "+(a *20))
val left: Int=10
val right: Int =20
println("sum = "+Sum(left,right))
println("max = "+Max(left,right))
println("min = "+Min(left,right))
println("max2 = "+Max2(left,right))
println("max3 = "+Max3(left,right))
println("测试when()使⽤"+" \n")
println("Tom's score is = "+getScore("Tom"))
println("Tom's score is = "+getScore2("TomCat"))
println("Tom's score is = "+getScore2("TomJack"))
println("测试Number"+" \n")
checkNumber(d)
checkNumber2(d)
println("测试for循环0..10表⽰闭区间[0,10] "+" \n")
TestForClose()
println("测试for循环0 unitl 10表⽰前开后闭[0,10) "+" \n")
TestForOpen()变速轮
println("测试for循环0 until 10 step 2表⽰设置步长位2 "+" \n")
TestForOpenAndStep()
println("测试for循环 downTo 表⽰从某个值减到某个值"+" \n")
TestDownTo()
println("测试Person类"+" \n")
val p =Person("jack",20)
p.name ="jack"
p.age =20
p.eat()
println("测试继承和构造函数"+" \n")
val student =Student("1870649",90,"Tom",20)
val student1 =Student2()
student1.printSome()
val student2 =Student2("jack",10)
student2.printSome()
val student3 =Student2("1870649",98,"jack",20)
student3.printSome()
println("测试接⼝"+" \n")
var studentX =Student3("JACK",20)
studentX.answerQuestion()
println("测试单例模式---使⽤JAVA创建"+" \n")
val singleTon = Instance()
println("测试单例模式---使⽤KOTLIN创建"+" \n")
KotlinSingleton.singleTest()
println("测试集合list---使⽤KOTLIN创建"+" \n")
val listFruit =listOf("Apple","balana","orange")//使⽤mutableListOf可以对集合进⾏增改删除操作for(fruit in listFruit)
{
}
val newList = listFruit.filter{ it.length <=5}.map{ it.toUpperCase()}//使⽤filter筛选出长度⼩于5的⽔果并转化成⼤写
for(fruit in newList)
{
println(fruit)
}
println("测试集合set，没有重复元素---使⽤KOTLIN创建"+" \n")
val setFruit =mutableSetOf("apple","pear","orabge")
setFruit.add("strewberry")
for(fruit in setFruit)
{
println(fruit)
}
println("测试集合map---使⽤KOTLIN创建"+" \n")
val mapFruit =mutableMapOf("Apple"to1,"orange"to2,"strawberry"to3)
mapFruit["pear"]=4
mapFruit.put("Apple",2)//键值不能重复
for((fruit,number)in mapFruit)
{
println("fruit is $fruit , number is $number")//KOTLIN写法等同于：println("fruit is " + fruit + " number is " + number) }
println("判空辅助?. "+" \n")
val isNullStringTest: String =""
println(getLength(isNullStringTest))
珍珠岩防火门芯板println("使⽤函数参数默认值 "+" \n")
defaultVale("hello")
}
fun defaultVale(str: String,i: Int =10)
{
println("string is + $str , number is $i .")
}
fun getLength(str : String)= str?.length?:0
fun Sum(a:Int,b:Int): Int{
return a+b
}
fun Max(a:Int,b:Int):Int
{
return max(a,b)
}
fun Max2(a: Int,b: Int):Int
{
var value =0
if(a>b)
value = a
else
value = b
return value
}
fun Max3(a: Int,b: Int):Int =if(a>b) a else b
fun Min(a: Int,b:Int):Int =min(a,b)
fun getScore(name: String)=when(name){ "Tom"->86
"Jack"->99
else->0
}
fun getScore2(name: String)=when
{
name.startsWith("Tom")->98
name =="Tom"->98
name =="Jack"->95
else->0
}
fun checkNumber(number: Number)
{
when(number)
{
is Int ->println("number is int")
is Double ->println("number is double")
else->println("number is not support")
}
}
fun checkNumber2(number: Number)=when
{
number is Int ->println("number is int")
number is Double ->println("number is double") else->println("number is not support")
}
fun TestForClose()
{
for(i in0..10)
println(i)
}
fun TestForOpen(){
for(i in0 until 10)
println(i)
}
fun TestForOpenAndStep(){
for(i in0 until 10 step 2)
println(i)
}
fun TestDownTo()
{
gis地图制作for(i in10 downTo 1)
{
println(i)
}
}
创建单例模式⽂件KotlinSingleton.kt
app
object KotlinSingleton {
fun singleTest()
{
println("this is a singleTon designing by Kotlin language") }
}
创建Person.kt⽂件
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