//字符串
        //1.初始化字符串
        //1.1通过字面量赋值的方式初始化字符串
        let tempStrig = "this is temp string"

        let tempStrig = "this is TEMP string"
        //字母大小写
        print(tempStrig.uppercased())
        print(tempStrig.lowercased())

        //1.2通过创建String实例化的方法初始化字符串
        let anoutherString = String()
        
        //2.获取字符串长度
        let string = "晚上去跑步,go"
        //2.1utf8 获取字节
        let leng = string.lengthOfBytes(using: String.Encoding.utf8)
        print(leng)
        
        //2.2获取字符长度,大多数情况下这个
        let leng2 = string.characters.count
        print(leng2)
        
        //2.3字符串遍历
        for char in string.characters{
            print(char)
        }
        
        //3 连接字符串和字符
        //3.1加法赋值连接字符串
        var varStr = "qq"
        varStr += ".com"
        print(varStr)
        //3.2 加法预算符连接字符串
        let string1 = "Hello"
        let string2 = "World"
        var string3 = string1 + string2
        print(string3)
        
        //追加字符
        string3.append("!")
        
        //format 拼接字符串
        let timeString = String(format:"%@,%d%@","现在",6,"点")
        print(timeString)

//字符串截取
        let swiftString = "好喜欢!!!"
        //将swiftString 转换为OC 的字符串使用,根据范围来截取字符串
        let subString1 = (swiftString as NSString).substring(with: NSMakeRange(1, 3))
        print(subString1)
        
        //截取下标2 之前的字符
        let subString2 = (swiftString as NSString).substring(to: 2)
        print(subString2)
        //截取下标2 之后(含有2)
        let subString3 = (swiftString as NSString).substring(from: 2)
        print(subString3)
        
        var insertStr = "明天星期天"
        
        //插入
        //字符串最后
        insertStr.insert("a", at: insertStr.endIndex)
         print(insertStr)
        //字符串最前
        insertStr.insert("a", at: insertStr.startIndex)
         print(insertStr)
        //在指定位置插入
        insertStr.insert("g", at: insertStr.index(before: insertStr.index(insertStr.startIndex, offsetBy: 3)))
        print(insertStr)
        
        //移除指定下标字符
        insertStr.remove(at: insertStr.index(before: insertStr.index(insertStr.startIndex, offsetBy: 1)))
        print(insertStr)

        //系统提供的方法挺多的,大家有兴趣可以多看看

 //字符串比较
        //比较字符是否相同
        let s1 = "好的"
        let s2 = "好的"
        if s1 == s2 {
            print("s1 == s2")
        }else{
            print("s1 != s2")
        }
        
        let s3:NSString = "ok"
        let s4:NSString = "ok!"
        if s3.isEqual(to: s4 as String) {
            print("s3 == s4")
        }else{
            print("s3 != s4")
        }
        
        //比较字符串的前缀,后缀
        let array = ["do.docx","good.docx","name.docx","data.json","good.json"]
        for d in array {
            if d.hasPrefix("good"){
                print("前缀为good:\(d)")
            }
        }
        
        for d in array {
            if d.hasSuffix(".json"){
                print("后缀为.json:\(d)")
            }
        }