Louisyong9527 / kotlin-Note

kotlin note

kotlin-Note

kotlin note

kotlin基本数据类型6种：Byte Short Int Float Long Double java基本数据类型8种： byte short int float long double char boolean

运算符

kotlin中无三元运算符，用 if(a>b) a else b 代替

类型检测&类型转换

is

if (obj is String) = return obj.length // obj 在该条件分支内自动转换成 String

as

val x: String = y as String //若y为null，则抛出异常

val x: String? = y as String? //不会抛出异常

val x: String? = y as? String //as?在失败时返回 null

for循环 可以循环遍历任何提供了迭代器的对象

迭代: for (item in collection) print(item)

val items = listOf("apple", "banana", "kiwifruit") for (index in items.indices) { println("item at $index is ${items[index]}") }

通过索引遍历数组或list
for (i in array.indices) { println(array[i]) }

for循环迭代 val numbers = listOf("one", "two", "three", "four") for (item in numbers) { println(item) }

forEach迭代 val numbers = listOf("one", "two", "three", "four") numbers.forEach { println(it) }

标准迭代： val numbers = listOf("one", "two", "three", "four") val numbersIterator = numbers.iterator() while (numbersIterator.hasNext()) { println(numbersIterator.next()) }