Kotlin基本使用二

按照开发文档敲了一遍，根据打印值对其中的使用进行了简单注释

package net.edaibu.kotlintest/** * Created by ${GEQIPENG} on 2017/5/20. */fun main(args: Array<String>) {    println("for 循环_______________________")    //for 循环遍历    val items = listOf("apple", "orange", "banana")    for (item in items) {        println(item)    }    //通过索引遍历    for (index in items.indices)        println("item in $index is ${items[index]}")    println("while循环__________________________________")    //while 循环    val itemList = listOf("red", "green", "blue", "yellow")    var index = 0    while (index < itemList.size) {        println("color in $index is ${itemList[index]}")        index++    }    println("when表达式__________________________")    //when 表达式    fun describe(objects: Any): String =            when (objects) {                1 -> "one"                2 -> "two"                3 -> "three"                4 -> "four"                5 -> "five"                else -> "unKnown"            }    println(describe(1))    println(describe(6))    println("range使用_____________________________")    val x = 10    val y = 9    if (x in 1..y + 1) {        println("$x in range")    }    println("范围迭代遍历___________________________________")    for (x in 1..20) {        print("$x ,")    }    println()    println("___________________________________")    val itemList2 = listOf("001", "002", "003", "004", "005")    if (-1 !in 1..itemList2.size) {        println("-1 not in itemList2")    }    if (itemList2.size !in itemList2.indices) {        println("itemList2 size out of itemList2 indices")    }    println("步进模式判断_____________________________________")    //步进模式就是每几个单位显示一次,我这里step后写的3，输出1,4,7,10    for (x in 1..10 step 3) {        print("$x ,")    }    println()    println("集合的使用________________________________")    println("list集合")        //遍历输出    val listItems = listOf("orange", "apple", "banana")    for (item in listItems) {        print("$item   ")    }    println()    println("set 集合")    //注意when使用时优先匹配第一个输出，一旦输出，后面的将不再输出    val setItems = setOf("北京", "天津", "上海", "广州", "深圳")    when {        "北京" in setItems -> println("天安门")        "天津" in setItems -> println("狗不理包子")        "上海" in setItems -> println("东方电视塔")        "广州" in setItems -> println("小蛮腰")        "深圳" in setItems -> println("华侨城")        else -> println("搞错了地址")    }    println("lamada表达式___________________________________")    val listItems2 = listOf("orange", "apple", "banana","ok","okHttp","okIo")    listItems2.filter { it.startsWith("o")}//筛选以o开头的字符串            .sortedBy { it }//排序            .map {  it.toUpperCase()}//转换为大写字母            .forEach { println(it) }//遍历}