2.字符串String
最后更新于：2022-04-02 04:43:18
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 main
func 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 main
func main() {
s := `a
b\r\n\x00
c`
println(s)
}
~~~
输出结果:
~~~
a
b\r\n\x00
c
~~~
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 main
import (
"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 main
import (
"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 main
import (
"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 main
func 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 main
import (
"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 main
import (
"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 false
res1 is true
~~~
判断是不是以某个字符串结尾
~~~
package main
import (
"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 false
res1 is true
~~~
判断str在s中首次出现的位置，如果没有返回-1
~~~
package main
import (
"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 4
res1 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 main
import (
"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 7
res1 is -1
~~~
字符串替换
~~~
package main
import (
"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 golang
res1 is hello golang world
~~~
求str含s的次数
~~~
package main
import (
"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 3
countTime1 is 0
~~~
重复 n 次 str
~~~
package main
import (
"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 main
import (
"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 main
import (
"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 main
import (
"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 main
import (
"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 main
import (
"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 main
import (
"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 main
import (
"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 main
import (
"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 main
import (
"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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