字符串是不可变值类型，内部用指针指向 UTF-8 字节数组。

• 默认值是空字符串 ""。• 用索引号访问某字节，如 s[i]。• 不能用序号获取字节元素指针，&s[i] 非法。 • 不可变类型，无法修改字节数组。• 字节数组尾部不包含 NULL。

使用索引号访问字符 (byte)。

package mainfunc main() {    s := "abc"    println(s[0] == '\x61', s[1] == 'b', s[2] == 0x63)}

输出结果:

true true true

使用 " ` " 定义不做转义处理的原始字符串，支持跨行。

package mainfunc main() {    s := `ab\r\n\x00c`    println(s)}

输出结果:

ab\r\n\x00c

连接跨行字符串时，"+" 必须在上一行末尾，否则导致编译错误。

package mainimport (    "fmt")func main() {    s := "Hello, " +        "World!"    // s2 := "Hello, "    // +"World!"     //./main.go:11:2: invalid operation: + untyped string    fmt.Println(s)}

支持用两个索引号 ([]) 返回子串。 串依然指向原字节数组，仅修改了指针和 度属性。

package mainimport (    "fmt")func main() {    s := "Hello, World!"    s1 := s[:5]  // Hello    s2 := s[7:]  // World!    s3 := s[1:5] // ello    fmt.Println(s, s1, s2, s3)}

输出结果：

Hello, World! Hello World! ello

单引号字符常量表示 Unicode Code Point， 持 \uFFFF、\U7FFFFFFF、\xFF 格式。
对应 rune 类型，UCS-4。

package mainimport (    "fmt")func main() {    fmt.Printf("%T\n", 'a')    var c1, c2 rune = '\u6211', '们'    println(c1 == '我', string(c2) == "\xe4\xbb\xac")}

输出结果:

int32    // rune 是 int32 的别名 true true

要修改字符串，可先将其转换成 []rune 或 []byte，完成后再转换为 string。无论哪种转换，都会重新分配内存，并复制字节数组。

package mainfunc main() {    s := "abcd"    bs := []byte(s)    bs[1] = 'B'    println(string(bs))    u := "电脑"    us := []rune(u)    us[1] = '话'    println(string(us))}

输出结果:

aBcd电话

for 循环遍历字符串时，也有 byte 和 rune 两种方式。

package mainimport (    "fmt")func main() {    s := "abc汉字"    for i := 0; i < len(s); i++ { // byte        fmt.Printf("%c,", s[i])    }    fmt.Println()    for _, r := range s { // rune        fmt.Printf("%c,", r)    }    fmt.Println()}

输出结果:

a,b,c,æ,±,�,å,­,�,a,b,c,汉,字,

string的底层布局

字符串处理：

判断是不是以某个字符串开头

package mainimport (    "fmt"    "strings")func main() {    str := "hello world"    res0 := strings.HasPrefix(str, "http://")    res1 := strings.HasPrefix(str, "hello")    fmt.Printf("res0 is %v\n", res0)    fmt.Printf("res1 is %v\n", res1)}

输出结果：

res0 is falseres1 is true

判断是不是以某个字符串结尾

package mainimport (    "fmt"    "strings")func main() {    str := "hello world"    res0 := strings.HasSuffix(str, "http://")    res1 := strings.HasSuffix(str, "world")    fmt.Printf("res0 is %v\n", res0)    fmt.Printf("res1 is %v\n", res1)}

输出结果：

res0 is falseres1 is true

判断str在s中首次出现的位置，如果没有返回-1

package mainimport (    "fmt"    "strings")func main() {    str := "hello world"    res0 := strings.Index(str, "o")    res1 := strings.Index(str, "i")    fmt.Printf("res0 is %v\n", res0)    fmt.Printf("res1 is %v\n", res1)}

输出结果：

res0 is 4res1 is -1

判断str在s中最后一次出现的位置，如果没有返回-1

package mainimport (    "fmt"    "strings")func main() {    str := "hello world"    res0 := strings.LastIndex(str, "o")    res1 := strings.LastIndex(str, "i")    fmt.Printf("res0 is %v\n", res0)    fmt.Printf("res1 is %v\n", res1)}

输出结果：

res0 is 7res1 is -1

字符串替换

package mainimport (    "fmt"    "strings")func main() {    str := "hello world world"    res0 := strings.Replace(str, "world", "golang", 2)    res1 := strings.Replace(str, "world", "golang", 1)    //trings.Replace("原字符串", "被替换的内容", "替换的内容", 替换次数)    fmt.Printf("res0 is %v\n", res0)    fmt.Printf("res1 is %v\n", res1)}

输出结果：

res0 is hello golang golangres1 is hello golang world

求str含s的次数

package mainimport (    "fmt"    "strings")func main() {    str := "hello world world"    countTime0 := strings.Count(str, "o")    countTime1 := strings.Count(str, "i")    fmt.Printf("countTime0 is %v\n", countTime0)    fmt.Printf("countTime1 is %v\n", countTime1)}

输出结果：

countTime0 is 3countTime1 is 0

重复 n 次 str

package mainimport (    "fmt"    "strings")func main() {    str := "hello world "    res0 := strings.Repeat(str, 0)    res1 := strings.Repeat(str, 1)    res2 := strings.Repeat(str, 2)    // strings.Repeat("原字符串", 重复次数)    fmt.Printf("res0 is %v\n", res0)    fmt.Printf("res1 is %v\n", res1)    fmt.Printf("res2 is %v\n", res2)}

输出结果：

res0 is res1 is hello world res2 is hello world hello world 

str 转为大写

package mainimport (    "fmt"    "strings")func main() {    str := "hello world "    res := strings.ToUpper(str)    fmt.Printf("res is %v\n", res)}

输出结果：

res is HELLO WORLD 

str 转为小写

package mainimport (    "fmt"    "strings")func main() {    str := "HELLO WORLD "    res := strings.ToLower(str)    fmt.Printf("res is %v\n", res)}

输出结果：

res is hello world 

去掉 str 首尾的空格

package mainimport (    "fmt"    "strings")func main() {    str := "     hello world     "    res := strings.TrimSpace(str)    fmt.Printf("res is %v\n", res)}

去掉字符串首尾指定的字符

package mainimport (    "fmt"    "strings")func main() {    str := "hi , hello world , hi"    res := strings.Trim(str, "hi")    fmt.Printf("res is %v\n", res)}

输出结果：

res is  , hello world , 

去掉字符串首指定的字符

package mainimport (    "fmt"    "strings")func main() {    str := "hi , hello world , hi"    res := strings.TrimLeft(str, "hi")    fmt.Printf("res is %v\n", res)}

输出结果：

res is  , hello world , hi

去掉字符串尾指定的字符

package mainimport (    "fmt"    "strings")func main() {    str := "hi , hello world , hi"    res := strings.TrimRight(str, "hi")    fmt.Printf("res is %v\n", res)}

输出结果：

res is hi , hello world , 

返回str空格分隔的所有子串的slice,

package mainimport (    "fmt"    "strings")func main() {    str := "hello world ，hello golang"    res := strings.Fields(str)    fmt.Printf("res is %v\n", res)}

输出结果：

res is [hello world ，hello golang]

返回str 指定字符分隔的所有子串的slice

package mainimport (    "fmt"    "strings")func main() {    str := "hello world ，hello golang"    res := strings.Split(str, "o")    fmt.Printf("res is %v\n", res)}

输出结果：

res is [hell  w rld ，hell  g lang]

用指定字符将 string 类型的 slice 中所有元素链接成一个字符串

package mainimport (    "fmt"    "strings")func main() {    str := []string{"hello", "world", "hello", "golang"}    res := strings.Join(str, "++")    fmt.Printf("res is %v\n", res)    /*        num := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}        res1 := strings.Join(num, "++")        //  cannot use num (type []int) as type []string in argument to strings.Join        fmt.Println(res1)    */}

输出结果：

res is hello++world++hello++golang

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