kotlin字符串方法

以下是一些常用的 String 方法示例：

1.获取字符串长度：

val str = "Hello, Kotlin"
val length = str.length

2.字符串比较：

val str1 = "apple"
val str2 = "banana"
val compareResult = str1.compareTo(str2)

3.子字符串：

val str = "Hello, Kotlin"
val subStr = str.substring(7, 12) // 提取子字符串 "Kotlin"

4.大小写转换

val str = "Kotlin Programming"
val lowerCase = str.toLowerCase()
val upperCase = str.toUpperCase()

5.判断前缀和后缀：

val str = "Kotlin Programming"
val startsWith = str.startsWith("Kotlin")
val endsWith = str.endsWith("Programming")

6.替换字符串

val str = "Hello, Java"
val replacedStr = str.replace("Java", "Kotlin")

7.拆分字符串：

val str = "apple,banana,orange"
val fruits = str.split(",")

8.去除空格：

val str = "  Kotlin Programming   "
val trimmedStr = str.trim() // 去除前导和尾部空格

9.字符串连接：

val str1 = "Hello"
val str2 = "Kotlin"
val combinedStr = str1 + " " + str2

10.查找子字符串的位置：

val str = "Hello, Kotlin"
val index = str.indexOf("Kotlin") // 返回子字符串的起始位置

11.是否包含子字符串

val str = "Hello, Kotlin"
val contains = str.contains("Kotlin")

12.正则表达式匹配

val str = "Email: [e-mail]"
val isEmail = str.matches(Regex("[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,4}"))

13.格式化字符串

val name = "Alice"
val age = 30
val formattedStr = "Name: $name, Age: $age"

14.字符串分割成字符列表：

val str = "Kotlin"
val charList = str.toList()

15.字符串反转：

val str = "Kotlin"
val reversedStr = str.reversed()

16.字符串去重

val str = "aaabbbccc"
val uniqueStr = str.toSet().joinToString("")

17.检查字符串是否为空

val str = ""
val isEmpty = str.isEmpty()
val isBlank = str.isBlank() // 空格也算空

18.格式化输出

val name = "John"
val age = 25
println("Name: %s, Age: %d".format(name, age))