package main

 import (

   "strconv"

   "fmt"

   "strings"

 )

 func main() {

     str := "Hello World test!"

     result := strings.Replace(str, "World", "golang", )

     fmt.Println(result)

     count := strings.Count(str, "o")

     fmt.Println(count)

     result = strings.Repeat(str, )

     fmt.Println(result)    

     result = strings.ToUpper(str)

     fmt.Println(result)    

     result = strings.ToLower(str)

     fmt.Println(result)    

     result = strings.TrimSpace(str)

     fmt.Println("trimSpace:" ,result)

     result = strings.Trim(str, " \n\r")

     fmt.Println("trim:" ,result)

     result =  strings.TrimLeft(str, " \n\r")

     fmt.Println("trimleft:" ,result)

     result =  strings.TrimRight(str, " \n\r")

     fmt.Println("trimright:" ,result)

     splitResult := strings.Fields(str)

     for i := ; i < len(splitResult); i++ {

         fmt.Println(splitResult[i])

     }

     str2 := strings.Join(splitResult, "l")

     fmt.Println("join:", str2)

     str2 = strconv.Itoa()

     fmt.Println("itoa:", str2)

     number, err := strconv.Atoi(str2)

     if err != nil {

         fmt.Println("can not convert to int,", err)

         return

     }

     fmt.Println("number:", number)

 }