kotlin简单学习

fun main(args: Array<String>){

    var arr=arrayOf("333",1,2,"fuck","hello",true,1.5f);

    println("Hello Worldxxx! arr firstelement￥${arr[0]}");
    val language = if (args.size == 0) "EN" else args[0]
    var switchResult= if(arr.size==0 )  "first"  else if(arr.size==7) "7"   else if(arr.size==8) "8" else "xxx";
   var whenresult= when(switchResult){
        "first"->"this is white"
        "7"->println("what 's that fuck?")
//        "7"->"this is 7 arr"
        "6"-> "finr 6666"
//        "6"-> println("zheli you 7ge ")
       else->"error< result:"+switchResult+",and element.size:"+arr.size
    }
    println("whenresult: if return return fucktion , result str:kotlin.Unit"+whenresult)
    for (name in arr) {
        println("name:"+name+",or ${name}")
    }
    
}

上面比较好奇的是 7->println()这个逻辑，为毛可以接受一个函数非字符串，发现这个函数返回的是kotlin.Unit 字符串。

for循环

  var arr=arrayOf("333",1,2,"fuck","hello",true,1.5f);

    for (name in arr) {
        println("name:"+name+",or ${name}")
    }

 for (index in arr.indices){
      println("index:"+index+",value:${arr[index]}")
  }

数组元素是否包含的判断

···
if ("aaa" in array) // collection.contains(obj) is called
println("Yes: array contains aaa")

···

for循环范围

    for (a in 1..5)
        print("${a} ")

when 的用法

fun describeWhen(obj: Any): String =  when (obj) {
            1          -> "Int"
            "Hello"    -> "Greeting"
            is Long    -> "Long"
            is Boolean    -> "Boolean"
            !is String -> "Not a string"
            else       -> "Unknown"
        }

println(describeWhen(false)); //输出Boolean这个函数可以放到任意函数里面去。