Kotlin中字符串处理

println("明年${age + 1}岁时，$name 将在 $city 庆祝生日。")

val str = "Hello"
val length = str.length // 返回 5

val str = "Hello, World!"
val sub = str.substring(7) // 返回 "World!"

val str = "Hello, World!"
val contains = str.contains("World") // 返回 true

val str = "Hello, Kotlin!"
val newStr = str.replace("Kotlin", "World") // 返回 "Hello, World!"

val str = "Hello"
val upper = str.toUpperCase() // 返回 "HELLO"
val lower = str.toLowerCase() // 返回 "hello"

val str = "  Hello, World!  "
val trimmed = str.trim() // 返回 "Hello, World!"

val str = "apple,banana,orange"
val fruits = str.split(",") // 返回 ["apple", "banana", "orange"]

val str = "42"
val num = str.toInt() // 返回 42

val str = ""
if (str.isEmpty()) {
    // 字符串为空
} else {
    // 字符串不为空
}

val str: String? = null
if (str.isNullOrEmpty()) {
    // 字符串为空或为null
} else {
    // 字符串不为空且不为null
}

val str = "   "
if (str.isNullOrBlank()) {
    // 字符串为null、空字符串或只包含空白字符
} else {
    // 字符串不为空且不只包含空白字符
}