//NSString stringWithFormat, stringWithString, stringWithUTF8String
        NSString *s1 = [NSString stringWithFormat:@"苹果fans"];
        NSLog(@"s1: %@", s1);

        NSString *s2 = [NSString stringWithString:@"上海 developer"];
        NSLog(@"s2: %@", s2);

        NSString *s3 = [NSString stringWithUTF8String:"我是utf8字符串类型"];
        NSLog(@"s3: %@", s3);


//NSString  stringByAppendingFormat
        int y = 2012;
char *c = "learn iOS";  //不能为中文
        NSString *s4 = [NSString stringWithFormat:@"标记"];
        NSString *s5 = [s4 stringByAppendingFormat:@"%d年%s", y, c];
        NSLog(@"s5: %@", s5);


//NSString length, traverse
        NSString *s6 = [NSString stringWithFormat:@"苹果iOS"];
        NSInteger len = [s6 length];
        NSLog(@"s6's length is %ld", len);

for(int i=0; i <len; i++){
char c1 = [s6 characterAtIndex:i];
            NSLog(@"s6 - index %d, char is %c", i, c1);
        }


//NSString isEqualToString
        NSString *s7 = [NSString stringWithFormat:@"google"];
        NSString *s8 = [NSString stringWithFormat:@"google"];
        NSString *s9 = [NSString stringWithFormat:@"apple"];  //microsoft, Google
        
if ([s7 isEqualToString:s8]) {
            NSLog(@"s7,s8: same");
        }else
            NSLog(@"s7,s8: not same");


//NSString compare NSCaseInsensitiveSearch, NSNumbericSearch, NSLiteralSearch
        switch ([s7 compare:s9
                    options:NSCaseInsensitiveSearch]) {
case NSOrderedSame:
                NSLog(@"s7 compare to s9: same");
break;
case NSOrderedAscending:
                NSLog(@"s7 compare to s9: asc");
break;
case NSOrderedDescending:
                NSLog(@"s7 compare to s9: desc");
break;
        }

//NSString hasPrefix, hasSuffix
        NSString *str10 = [NSString stringWithFormat:@"apple 粉丝"];
if ([str10 hasPrefix:@"apple"]) {
            NSLog(@"str10 has prefix \"apple\"");
        }else
            NSLog(@"str10 has no prefix \"apple\"");

if ([str10 hasSuffix:@"粉丝"]) {
            NSLog(@"str10 has suffix \"粉丝\"");
        }else
            NSLog(@"str10 has no suffix \"粉丝\"");

//NSString substringToIndex, substringFromIndex, substringWithRange
        NSString *str11 = [NSString stringWithFormat:@"我I am an apple 粉丝"];
        NSString *str12 = [str11 substringToIndex:5];
        NSLog(@"str12: %@", str12);
        NSString *str13 = [str12 substringFromIndex:1];
        NSLog(@"str13: %@", str13);
        NSString *str14 = [str11 substringWithRange:[str11 rangeOfString:@"apple"]];
        NSLog(@"str14: %@", str14);


//NSString uppercaseString, lowercaseString, capitalizedString
        NSString *str15 = [NSString stringWithFormat:@"apple FANS"];
        NSString *str16 = [str15 uppercaseString];
        NSString *str17 = [str15 lowercaseString];
        NSString *str18 = [str15 capitalizedString];
        NSLog(@"str16: %@", str16);
        NSLog(@"str17: %@", str17);
        NSLog(@"str18: %@", str18);

//NSString stringByReplacingOccurrencesOfString, stringByReplacingCharactersInRange
        NSString *str19 = [NSString stringWithFormat:@"orange, apple, banana, pear"];
        NSString *str20 = [str19 stringByReplacingOccurrencesOfString:@"," withString:@";"];
        NSLog(@"str20: %@", str20);

        NSRange range = [str19 rangeOfString:@"apple"];
        NSLog(@"location is %ld, length is %ld", range.location, range.length);
        NSString *str21 = [str19 stringByReplacingCharactersInRange:range
                                                         withString:@"peach"];
        NSLog(@"str21: %@", str21);

//NSString 强制转换
        NSString *s22 = @"2012";
        NSInteger year1 = [s22 integerValue];
        NSLog(@"NSInteger: %ld", year1);

int year2 = [s22 intValue];
        NSLog(@"int: %d", year2);

        s1 = @"3.1415926";
double d = [s1 doubleValue];
        NSLog(@"double: %f", d);

float f = [s1 floatValue];
        NSLog(@"float: %f", f);

//NSNotFound
        NSString *str23 =[NSString stringWithFormat:@"apple"];
        NSRange range = [str23 rangeOfString:@"ibm"];

if (range.location == NSNotFound) {
            NSLog(@"not found");
        }else
        {
            NSLog(@"location: %ld", range.location);
        }

[[NSString alloc] initWithFormat:@"%d",10];

[NSString alloc] initWithCString:@"字符串内容"]

[str replaceOccurrencesOfString:@"1" withString:@"222" options:NSLiteralSearch range:NSMakeRange(0, [str length])];

NSMutableString *String;
  String = [NSMutableString stringWithCapacity:40];

 NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
 [String1 appendFormat:[NSString stringWithFormat:@", I will be adding some character"]];

 NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
 [String1 deleteCharactersInRange:NSMakeRange(0, 5)];

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 insertString:@"Hi! " atIndex:0];

 NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
 [String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];

NSString *String1 = @"NSStringInformation.txt";
[String1 hasPrefix:@"NSString"] = = 1 ?  NSLog(@"YES") : NSLog(@"NO");
[String1 hasSuffix:@".txt"] = = 1 ?  NSLog(@"YES") : NSLog(@"NO");

NSString *list = @"Norman, Stanley, Fletcher";
NSArray *listItems = [list componentsSeparatedByString:@", "];
//listItems包含了：{ @"Norman", @"Stanley", @"Fletcher" }.

NSRange range = [@"字符串--A" rangeOfString:“是否包含--B”];

if (range.location == NSNotFound)

{//不包含
}
else
{//包含
}