安卓开发之Kotlin(2)_安卓kotiln helloworld

kotlin入门学习-勿喷

fun main(args:Array<String>) {
	println("HelloWorld");
}
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05_kotlin变量与输出_01

05_kotlin变量与输出_02

变量的声明与使用

fun main(args:Array<String>) {
	//println("HelloWorld");
	var name = "张三"
	println(name)
}

打印： 张三

var name = "张三"
name = "lisi"
println(name)

打印： lisi

错误：The integer literal does not conform to the expected type String

var name = "张三"
name = "lisi"
name = 8
println(name)
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06_kotlin二进制基础_01

07_kotlin变量和常量&类型推断_01

变量		var number1 = "变量，可赋值"

错误：The integer literal does not conform to the expected type Int

var i = 18
i = 19
i = 999999999999999999
var k:Byte = 25 (-127~128)

智能类型推断	

var j = 999999999999999999

显式指定类型：

var i:Int = 18
var j:Long = 999999999999999999
var s:String = "haha"

错误：This variable must either have a type annotation or be initialized
var a 

改：
var a:Int

常量		val number2 = "常量，只读"
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08_kotlin变量取值范围_01

val aByte:Byte = Byte.MAX_VALUE
val bByte:Byte = Byte.MIN_VALUE
println("最大值:"+ aByte)
println("最小值:"+ bByte)

val aLong:Long = Long.MAX_VALUE
val bLong:Long = Long.MIN_VALUE
println("最大值:"+ aLong)
println("最小值:"+ bLong)

val aInt:Int = 0b0011
println("aInt:"+ aInt)
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09_kotlin函数入门_01

10_kotlin语言boolean_01

var num1 = 4
val num2 = 6
println(num1 < num2)

var num3 = Math.sqrt(5.0) - Math.sqrt(4.0)
var num4 = Math.sqrt(4.0) - Math.sqrt(3.0)
println(num3 - num4)

var num5 = Math.pow(2.0, 100.0)
var num6 = Math.pow(3.0, 75.0)
println(num5 < num6)
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11_kotlin命令行交互式终端_01

12_kotlin函数加强_01

12_kotlin函数加强_02

fun main(args: Array<String>) {
    var a = 8
    var b = 2
    println("a+b="+ plus(a,b))
    println("a-b="+ sub(a,b))
    println("a*b="+ mutl(a,b))
    println("a/b="+ devide(a,b))
}

fun plus(a: Int, b: Int): Int {
    return a + b
}

fun sub(a: Int, b: Int): Int {
    return a - b
}

fun mutl(a: Int, b: Int): Int {
    return a * b
}

fun devide(a: Int, b: Int): Int {
    return a / b
}
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13_kotlin函数作业讲解_01

fun main(args: Array<String>) {
	var name = "张三"
	var personName = sayHello(name)
	println(personName)
}

fun sayHello(name: String): String {
    return "hello" + name
}

fun checkAge(age: Int): Boolean {
    if (age > 18) return true
  
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