了解标准库是一个非常好的学习语言的方法。接下里的一些列章节我们将详细研究标准库中的类型，方法，结合实际应用案例进行有趣的编程。

字符串处理是比较基础的库，我们从简单的库开始入门。

先看一下strings相关的类型和方法，大概分为通用方法部分和Builder，Reader，Replacer类型。

func Clone(s string) string
func Compare(a, b string) int
func Contains(s, substr string) bool
func ContainsAny(s, chars string) bool
func ContainsFunc(s string, f func(rune) bool) bool
func ContainsRune(s string, r rune) bool
func Count(s, substr string) int
func Cut(s, sep string) (before, after string, found bool)
func CutPrefix(s, prefix string) (after string, found bool)
func CutSuffix(s, suffix string) (before string, found bool)
func EqualFold(s, t string) bool
func Fields(s string) []string
func FieldsFunc(s string, f func(rune) bool) []string
func HasPrefix(s, prefix string) bool
func HasSuffix(s, suffix string) bool
func Index(s, substr string) int
func IndexAny(s, chars string) int
func IndexByte(s string, c byte) int
func IndexFunc(s string, f func(rune) bool) int
func IndexRune(s string, r rune) int
func Join(elems []string, sep string) string
func LastIndex(s, substr string) int
func LastIndexAny(s, chars string) int
func LastIndexByte(s string, c byte) int
func LastIndexFunc(s string, f func(rune) bool) int
func Map(mapping func(rune) rune, s string) string
func Repeat(s string, count int) string
func Replace(s, old, new string, n int) string
func ReplaceAll(s, old, new string) string
func Split(s, sep string) []string
func SplitAfter(s, sep string) []string
func SplitAfterN(s, sep string, n int) []string
func SplitN(s, sep string, n int) []string
func Title(s string) stringDEPRECATED
func ToLower(s string) string
func ToLowerSpecial(c unicode.SpecialCase, s string) string
func ToTitle(s string) string
func ToTitleSpecial(c unicode.SpecialCase, s string) string
func ToUpper(s string) string
func ToUpperSpecial(c unicode.SpecialCase, s string) string
func ToValidUTF8(s, replacement string) string
func Trim(s, cutset string) string
func TrimFunc(s string, f func(rune) bool) string
func TrimLeft(s, cutset string) string
func TrimLeftFunc(s string, f func(rune) bool) string
func TrimPrefix(s, prefix string) string
func TrimRight(s, cutset string) string
func TrimRightFunc(s string, f func(rune) bool) string
func TrimSpace(s string) string
func TrimSuffix(s, suffix string) string
type Builder
func (b *Builder) Cap() int
func (b *Builder) Grow(n int)
func (b *Builder) Len() int
func (b *Builder) Reset()
func (b *Builder) String() string
func (b *Builder) Write(p []byte) (int, error)
func (b *Builder) WriteByte(c byte) error
func (b *Builder) WriteRune(r rune) (int, error)
func (b *Builder) WriteString(s string) (int, error)
type Reader
func NewReader(s string) *Reader
func (r *Reader) Len() int
func (r *Reader) Read(b []byte) (n int, err error)
func (r *Reader) ReadAt(b []byte, off int64) (n int, err error)
func (r *Reader) ReadByte() (byte, error)
func (r *Reader) ReadRune() (ch rune, size int, err error)
func (r *Reader) Reset(s string)
func (r *Reader) Seek(offset int64, whence int) (int64, error)
func (r *Reader) Size() int64
func (r *Reader) UnreadByte() error
func (r *Reader) UnreadRune() error
func (r *Reader) WriteTo(w io.Writer) (n int64, err error)
type Replacer
func NewReplacer(oldnew ...string) *Replacer
func (r *Replacer) Replace(s string) string
func (r *Replacer) WriteString(w io.Writer, s string) (n int, err error)

本节我们将用一些实例代码研究以下7个函数的用法。
func Clone(s string) string
func Compare(a, b string) int
func Contains(s, substr string) bool
func ContainsAny(s, chars string) bool
func ContainsFunc(s string, f func(rune) bool) bool
func ContainsRune(s string, r rune) bool
func Count(s, substr string) int

package main

import (
    "fmt"
    "strings"
    "unsafe"
)

func main() {
    m := "hello this is strings."
    c := strings.Clone(m)
    // 判断相同指针，clone会创建新副本，因此这里返回false
    fmt.Println(unsafe.StringData(c) == unsafe.StringData(m))
    // 比较，返回0则相等
    fmt.Println(strings.Compare(c, m))
    // 是否包含hello字符串
    fmt.Println(strings.Contains(c, "hello"))
    // 是否含有xyzh中的任意一个字母
    fmt.Println(strings.ContainsAny(c, "xyzh"))
    // 是否有z字母
    fmt.Println(strings.ContainsFunc(c, func(a rune) bool {
        return a == 'z'
    }))
    // 是否有a字母
    fmt.Println(strings.ContainsRune(c, 97))
    // 字母i出现几次
    fmt.Println(strings.Count(c, "i"))
}
输出：
false
0
true
true
false
false
3