diff --git a/readme.md b/readme.md
index 36d540c..2877ea1 100644
--- a/readme.md
+++ b/readme.md
@@ -6,3 +6,9 @@ usage:
 ```bash
 go get git.sre.ink/go/gtool
 ```
+
+
+***
+https://github.com/duke-git/lancet
+
+lancet（柳叶刀）是一个全面、高效、可复用的go语言工具函数库。 lancet受到了java apache common包和lodash.js的启发。
\ No newline at end of file
diff --git a/str/assertion.go b/str/assertion.go
new file mode 100644
index 0000000..fcb50c3
--- /dev/null
+++ b/str/assertion.go
@@ -0,0 +1,14 @@
+package str
+
+// IsString check if the value data type is string or not.
+func (sst *Str) IsString(v any) bool {
+	if v == nil {
+		return false
+	}
+	switch v.(type) {
+	case string:
+		return true
+	default:
+		return false
+	}
+}
diff --git a/str/assertion_test.go b/str/assertion_test.go
new file mode 100644
index 0000000..b71e17b
--- /dev/null
+++ b/str/assertion_test.go
@@ -0,0 +1,17 @@
+package str
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestStr_IsString(t *testing.T) {
+	fmt.Println(StrTool.IsString("hello world!"))
+	fmt.Println(StrTool.IsString(123))
+	fmt.Println(StrTool.IsString(true))
+	fmt.Println(StrTool.IsString(nil))
+	fmt.Println(StrTool.IsString([]string{"hello", "world"}))
+	fmt.Println(StrTool.IsString(map[string]string{"hello": "world"}))
+	fmt.Println(StrTool.IsString(struct{}{}))
+
+}
diff --git a/str/covert.go b/str/covert.go
new file mode 100644
index 0000000..973eb20
--- /dev/null
+++ b/str/covert.go
@@ -0,0 +1,246 @@
+package str
+
+import (
+	"regexp"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Capitalize converts the first character of a string to upper case and the remaining to lower case.
+func (sst *Str) Capitalize(s string) string {
+	if len(s) == 0 {
+		return ""
+	}
+
+	out := make([]rune, len(s))
+	for i, v := range s {
+		if i == 0 {
+			out[i] = unicode.ToUpper(v)
+		} else {
+			out[i] = unicode.ToLower(v)
+		}
+	}
+
+	return string(out)
+}
+
+// CamelCase covert string to camelCase string.
+func (sst *Str) CamelCase(s string) string {
+	if len(s) == 0 {
+		return ""
+	}
+
+	res := ""
+	blankSpace := " "
+	regex, _ := regexp.Compile("[-_&]+")
+	ss := regex.ReplaceAllString(s, blankSpace)
+	for i, v := range strings.Split(ss, blankSpace) {
+		vv := []rune(v)
+		if i == 0 {
+			if vv[i] >= 65 && vv[i] <= 96 {
+				vv[0] += 32
+			}
+			res += string(vv)
+		} else {
+			res += sst.Capitalize(v)
+		}
+	}
+
+	return res
+}
+
+// UpperFirst converts the first character of string to upper case.
+func (sst *Str) UpperFirst(s string) string {
+	if len(s) == 0 {
+		return ""
+	}
+
+	r, size := utf8.DecodeRuneInString(s)
+	r = unicode.ToUpper(r)
+
+	return string(r) + s[size:]
+}
+
+// LowerFirst converts the first character of string to lower case.
+func (sst *Str) LowerFirst(s string) string {
+	if len(s) == 0 {
+		return ""
+	}
+
+	r, size := utf8.DecodeRuneInString(s)
+	r = unicode.ToLower(r)
+
+	return string(r) + s[size:]
+}
+
+// PadEnd pads string on the right side if it's shorter than size.
+// Padding characters are truncated if they exceed size.
+func (sst *Str) PadEnd(source string, size int, padStr string) string {
+	len1 := len(source)
+	len2 := len(padStr)
+
+	if len1 >= size {
+		return source
+	}
+
+	fill := ""
+	if len2 >= size-len1 {
+		fill = padStr[0 : size-len1]
+	} else {
+		fill = strings.Repeat(padStr, size-len1)
+	}
+	return source + fill[0:size-len1]
+}
+
+// PadStart pads string on the left side if it's shorter than size.
+// Padding characters are truncated if they exceed size.
+func (sst *Str) PadStart(source string, size int, padStr string) string {
+	len1 := len(source)
+	len2 := len(padStr)
+
+	if len1 >= size {
+		return source
+	}
+
+	fill := ""
+	if len2 >= size-len1 {
+		fill = padStr[0 : size-len1]
+	} else {
+		fill = strings.Repeat(padStr, size-len1)
+	}
+	return fill[0:size-len1] + source
+}
+
+// KebabCase covert string to kebab-case
+func (sst *Str) KebabCase(s string) string {
+	if len(s) == 0 {
+		return ""
+	}
+
+	regex := regexp.MustCompile(`[\W|_]+`)
+	blankSpace := " "
+	match := regex.ReplaceAllString(s, blankSpace)
+	rs := strings.Split(match, blankSpace)
+
+	var res []string
+	for _, v := range rs {
+		splitWords := splitWordsToLower(v)
+		if len(splitWords) > 0 {
+			res = append(res, splitWords...)
+		}
+	}
+
+	return strings.Join(res, "-")
+}
+
+// SnakeCase covert string to snake_case
+func (sst *Str) SnakeCase(s string) string {
+	if len(s) == 0 {
+		return ""
+	}
+
+	regex := regexp.MustCompile(`[\W|_]+`)
+	blankSpace := " "
+	match := regex.ReplaceAllString(s, blankSpace)
+	rs := strings.Split(match, blankSpace)
+
+	var res []string
+	for _, v := range rs {
+		splitWords := splitWordsToLower(v)
+		if len(splitWords) > 0 {
+			res = append(res, splitWords...)
+		}
+	}
+
+	return strings.Join(res, "_")
+}
+
+// ReverseStr return string whose char order is reversed to the given string
+func (sst *Str) ReverseStr(s string) string {
+	r := []rune(s)
+	for i, j := 0, len(r)-1; i < j; i, j = i+1, j-1 {
+		r[i], r[j] = r[j], r[i]
+	}
+	return string(r)
+}
+
+// Wrap a string with another string.
+func (sst *Str) Wrap(str string, wrapWith string) string {
+	if str == "" || wrapWith == "" {
+		return str
+	}
+	var sb strings.Builder
+	sb.WriteString(wrapWith)
+	sb.WriteString(str)
+	sb.WriteString(wrapWith)
+
+	return sb.String()
+}
+
+// Unwrap a given string from anther string. will change str value
+func (sst *Str) Unwrap(str string, wrapToken string) string {
+	if str == "" || wrapToken == "" {
+		return str
+	}
+
+	firstIndex := strings.Index(str, wrapToken)
+	lastIndex := strings.LastIndex(str, wrapToken)
+
+	if firstIndex == 0 && lastIndex > 0 && lastIndex <= len(str)-1 {
+		if len(wrapToken) <= lastIndex {
+			str = str[len(wrapToken):lastIndex]
+		}
+	}
+
+	return str
+}
+
+// SplitEx split a given string whether the result contains empty string
+func (sst *Str) SplitEx(s, sep string, removeEmptyString bool) []string {
+	if sep == "" {
+		return []string{}
+	}
+
+	n := strings.Count(s, sep) + 1
+	a := make([]string, n)
+	n--
+	i := 0
+	sepSave := 0
+	ignore := false
+
+	for i < n {
+		m := strings.Index(s, sep)
+		if m < 0 {
+			break
+		}
+		ignore = false
+		if removeEmptyString {
+			if s[:m+sepSave] == "" {
+				ignore = true
+			}
+		}
+		if !ignore {
+			a[i] = s[:m+sepSave]
+			s = s[m+len(sep):]
+			i++
+		} else {
+			s = s[m+len(sep):]
+		}
+	}
+
+	var ret []string
+	if removeEmptyString {
+		if s != "" {
+			a[i] = s
+			ret = a[:i+1]
+		} else {
+			ret = a[:i]
+		}
+	} else {
+		a[i] = s
+		ret = a[:i+1]
+	}
+
+	return ret
+}
diff --git a/str/covert_test.go b/str/covert_test.go
new file mode 100644
index 0000000..eaa836c
--- /dev/null
+++ b/str/covert_test.go
@@ -0,0 +1,74 @@
+package str
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestStr_Capitalize(t *testing.T) {
+	fmt.Println(StrTool.Capitalize("hello world!"))
+	//Hello world!
+	fmt.Println(StrTool.CamelCase("hello world!"))
+	//helloWorld!
+	fmt.Println(StrTool.CamelCase("test_ok"))
+	//testOk
+}
+
+func TestStr_UpperFirst(t *testing.T) {
+	fmt.Println(StrTool.UpperFirst("hello world!"))
+	//Hello world!
+	fmt.Println(StrTool.UpperFirst("test_ok"))
+	//Test ok
+	fmt.Println(StrTool.LowerFirst("Hello world!"))
+	//hello world!
+}
+
+func TestStr_PadEnd(t *testing.T) {
+	fmt.Println(StrTool.PadEnd("hello world!", 100, "*"))
+	fmt.Println(StrTool.PadEnd("hello world!", 100, "-"))
+	fmt.Println(StrTool.PadEnd("hello world!", 100, " "))
+	//hello world!****************************************************************************************
+	//hello world!----------------------------------------------------------------------------------------
+	//hello world!
+}
+func TestStr_PadStart(t *testing.T) {
+	fmt.Println(StrTool.PadStart("hello world!", 100, "*"))
+	fmt.Println(StrTool.PadStart("hello world!", 100, "-"))
+	fmt.Println(StrTool.PadStart("hello world!", 100, " "))
+
+	//****************************************************************************************hello world!
+	//----------------------------------------------------------------------------------------hello world!
+	//                                                                                        hello world!
+}
+
+func TestStr_KebabCase(t *testing.T) {
+	fmt.Println(StrTool.KebabCase("hello world!"))
+	//hello-world
+	fmt.Println(StrTool.KebabCase("test_ok"))
+	//test-ok
+}
+func TestStr_SnakeCase(t *testing.T) {
+	fmt.Println(StrTool.SnakeCase("hello world!"))
+	//hello_world
+	fmt.Println(StrTool.SnakeCase("test_ok"))
+	//test_ok
+}
+
+func TestStr_Wrap(t *testing.T) {
+	fmt.Println(StrTool.Wrap("hello world!", "100"))
+	//100hello world!100
+
+}
+func TestStr_Unwrap(t *testing.T) {
+	fmt.Println(StrTool.Unwrap("100hello world!100", "100"))
+	//hello world!
+}
+func TestStr_ReverseStr(t *testing.T) {
+	fmt.Println(StrTool.ReverseStr("hello world!"))
+	//!dlrow olleh
+}
+
+func TestStr_SplitEx(t *testing.T) {
+	fmt.Println(StrTool.SplitEx("hello world!", "world", true))
+	fmt.Println(StrTool.SplitEx("hello world!", "world", false))
+}
diff --git a/str/str.go b/str/hex.go
similarity index 100%
rename from str/str.go
rename to str/hex.go
diff --git a/str/str_test.go b/str/hex_test.go
similarity index 100%
rename from str/str_test.go
rename to str/hex_test.go
diff --git a/str/internal.go b/str/internal.go
new file mode 100644
index 0000000..267a88d
--- /dev/null
+++ b/str/internal.go
@@ -0,0 +1,40 @@
+package str
+
+import "strings"
+
+// splitWordsToLower split a string into worlds by uppercase char
+func splitWordsToLower(s string) []string {
+	var res []string
+
+	upperIndexes := upperIndex(s)
+	l := len(upperIndexes)
+	if upperIndexes == nil || l == 0 {
+		if s != "" {
+			res = append(res, s)
+		}
+		return res
+	}
+	for i := 0; i < l; i++ {
+		if i < l-1 {
+			res = append(res, strings.ToLower(s[upperIndexes[i]:upperIndexes[i+1]]))
+		} else {
+			res = append(res, strings.ToLower(s[upperIndexes[i]:]))
+		}
+	}
+	return res
+}
+
+// upperIndex get a int slice which elements are all the uppercase char index of a string
+func upperIndex(s string) []int {
+	var res []int
+	for i := 0; i < len(s); i++ {
+		if 64 < s[i] && s[i] < 91 {
+			res = append(res, i)
+		}
+	}
+	if len(s) > 0 && res != nil && res[0] != 0 {
+		res = append([]int{0}, res...)
+	}
+
+	return res
+}
diff --git a/str/internal_test.go b/str/internal_test.go
new file mode 100644
index 0000000..72818c4
--- /dev/null
+++ b/str/internal_test.go
@@ -0,0 +1,11 @@
+package str
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestInternal(tt *testing.T) {
+	fmt.Println(splitWordsToLower("Hello World,goodbye world!"))
+	fmt.Println(upperIndex("Hello World,goodbye world!"))
+}