//转换:大小字母转换 
        NSString *str5 = @"abcdefg hijklmn OPQRST UVWXYZ";
        
        //1.全部变大写字母
        NSLog(@"%@",[str5 uppercaseString]);
        
        //2.全部变小写字母
        NSLog(@"%@",[str5 lowercaseString]);
        
        //3.首字母大写 -> 每个单词的首字母大写,其他小写
        NSLog(@"%@",[str5 capitalizedString]);
        
        //str5还是原来的
        NSLog(@"%@",str5);
        
        //转化:基本数据类型
        NSString *str6 = @"10086";
        
        int intS = [str6 intValue];
        NSInteger inteS = [str6 integerValue];
        float floS = [str6 floatValue];
        double douS = [str6 doubleValue];
        BOOL boolS = [str6 boolValue];
        
        NSLog(@"%d",intS);
        NSLog(@"%ld",(long)inteS);
        NSLog(@"%fl",floS);
        NSLog(@"%f",douS);
        NSLog(@"%hhd",boolS);


2016-01-18 20:11:35.731 02NSString字符串[4039:618330] ABCDEFG HIJKLMN OPQRST UVWXYZ
2016-01-18 20:11:35.731 02NSString字符串[4039:618330] abcdefg hijklmn opqrst uvwxyz
2016-01-18 20:11:35.731 02NSString字符串[4039:618330] Abcdefg Hijklmn Opqrst Uvwxyz
2016-01-18 20:11:35.732 02NSString字符串[4039:618330] abcdefg hijklmn OPQRST UVWXYZ
2016-01-18 20:11:35.732 02NSString字符串[4039:618330] 10086
2016-01-18 20:11:35.732 02NSString字符串[4039:618330] 10086
2016-01-18 20:11:35.732 02NSString字符串[4039:618330] 10086.000000l
2016-01-18 20:11:35.732 02NSString字符串[4039:618330] 10086.000000
2016-01-18 20:11:35.732 02NSString字符串[4039:618330] 1