//初始化        //iniWithString------Returns an NSString object initialized by copying the characters from another given string.       // 返回一个NSString对象初始化复制来自另一个给定字符串的字符。        NSString *str = @"liuyafang";        NSString *str1 = [[NSString alloc] initWithString:str];        NSLog(@"str1 = %@", str1);                //计算字符串长度        //length------Returns the number of Unicode characters in the receiver.        //返回接收器中Unicode字符的数量        NSInteger count = [str length];   //可见长度        NSLog( @"%ld", count);                //initWithFormat:        //Returns an NSString object initialized by using a given format string as a template into which the remaining argument values are substituted.        //返回一个NSString对象初始化使用给定的格式字符串作为模板,其余参数值代替。        NSString *str2 = @"dapingmu";        NSString *str3 = [[NSString alloc] initWithFormat:@"liuyafang"];        NSLog(@"str2 = %@", str2);        NSLog(@"str3 = %@", str3);                //判断是否以指定字符开头或者结尾        BOOL pre = [str3 hasPrefix:@"liu"];        NSLog(@"%d", pre);                BOOL suf = [str3 hasSuffix:@"fang"];        NSLog(@"%d", suf);                //截取字符串的长度和起始位置－－－－Finds and returns the range of the first occurrence of a given string within the receiver.        //        NSRange rag =[str3 rangeOfString:@"liu"];        NSLog(@"length = %ld, lacation = %ld", rag.length, rag.location);                //截取从输入的起始位置开始输出        NSString *sub = [str3 substringFromIndex:3];        NSLog(@"%@", sub);        //截取到输入的位置并输出        NSString *subb = [str3 substringToIndex:3];        NSLog(@"%@", subb);        //截取一个范围字符串        NSRange aa = {0 , 4};        NSString *ran1 = [str3 substringWithRange:aa];        NSString *ran = [str3 substringWithRange:NSMakeRange(0, 5)];   //NSMakeRange(0, 5)  范围的起始位置和末尾位置        NSLog(@"%@", ran1);        NSLog(@"%@", ran);                //拼接字符串        NSString *str4 = @" very good !";        NSString *app = [str stringByAppendingString:str4];        NSLog(@"%@", app);                NSLog(@"%@",str);        NSString *b = [str stringByAppendingFormat:@"%@==%d", str,5];  //格式化拼接，，，有问题 ，，        NSLog(@"%@",b);        //替换字符串        NSString *rep = [str3 stringByReplacingOccurrencesOfString:@"ya" withString:@"xiao"];        NSLog(@"%@", rep);                //转换成小写的        NSString *lowe= [@"ljlkmJNnhjnHhhbhHnbjjbnghUKJkj" lowercaseString];        NSLog(@"%@", lowe);                //首字母转换成大写；        NSString *cap = [@"ad Hj  da  ajda ajdl la " capitalizedString];        NSLog(@"%@",cap);                         NSMutableString *mutabal = [NSMutableString stringWithCapacity:5];        NSLog(@"%@", mutabal);        NSMutableString *mutabal1 =[NSMutableString stringWithFormat:@"liuyafang"];        NSLog(@"%@", mutabal1);        //可变字符串拼接        //Adds a constructed string to the receiver.---添加一个构造字符串到接收方。        [mutabal1 appendFormat:@"good"];        NSLog(@"%@", mutabal1);                [mutabal1 appendFormat:@"%@", @"good"];        NSLog(@"%@", mutabal1);                //Adds to the end of the receiver the characters of a given string.--增加了接收机的最后一个给定字符串的字符。        [mutabal1 appendString:@"what!"];        NSLog(@"%@", mutabal1);                [mutabal1 stringByAppendingString:@"nimei"];        NSLog(@"----------%@", mutabal1);                        //删除范围字符串       // Removes from the receiver the characters in a given range.----删除来自接收者的角色在一个给定的范围内。        NSRange aaa = {0, 3};        [mutabal1 deleteCharactersInRange:aaa];        NSLog(@"%@", mutabal1);        //NSMakeRange-------Creates a new NSRange from the specified values.--创建一个新的NSRange指定值。        [mutabal1 deleteCharactersInRange:NSMakeRange(0, 3)];        NSLog(@"%@",mutabal1);                //Replaces the characters of the receiver with those in a given string.----替换字符的接收器与给定的字符串。         [mutabal1 setString:@"liu"];        NSLog(@"%@", mutabal1);                //作业1。。判断是否以EfGk结尾，如果是替换成WXYZ，然后转变成小写        NSString *exercise = @"aBcD_EfGk";        BOOL a1 = [exercise hasSuffix:@"EfGk"];        NSLog(@"%d", a1);        NSString *exer = [exercise stringByReplacingOccurrencesOfString:@"EfGk" withString:@"WXYZ"];        NSLog(@"---====>%@", exer);        NSString *exer1 = [exer lowercaseString];        NSLog(@"------>%@",exer1);                //作业1。2判断是都以png结尾，如果是替换成jpg，如果不是则添加.jpg                NSMutableString *page = [NSMutableString stringWithFormat:@"xiaoliu.png"];        BOOL aa11 = [page hasSuffix:@"png"];        NSLog(@"%d",aa11);        if ( aa11 == 1) {           NSString *page1 = [page stringByReplacingOccurrencesOfString:@"png" withString:@"jpg"];            NSLog(@"%@", page1);        }else{        [page appendString:@".jpg"];            NSLog(@"%@", page);        }                //数组初始化，，获取元素个数        NSArray *arr = [NSArray arrayWithObjects:@"ss",@"dd",@"aa", nil];        NSLog(@"%@", arr);        NSInteger con = [arr count];        NSLog(@"%ld", con);        // 根据对象获得所引致        //Returns the lowest index whose corresponding array value is equal to a given object.---        NSInteger dd = [arr indexOfObject:@"dd"];        NSLog(@"%ld", dd);        //根据所引致获得对象        //Returns the object located at the specified index.        NSArray *ppp = [arr objectAtIndex:0];        NSLog(@"0000000%@", ppp);                ///-------------可变数组--------------///                NSMutableArray *mutarr = [NSMutableArray arrayWithCapacity:5];        NSLog(@"%@", mutarr);        NSMutableArray *mt = [NSMutableArray arrayWithObjects:@"aaa", @"bbb", @"ccc", @"ddd", nil];        NSMutableArray *mm = [NSMutableArray arrayWithObjects:@"ee", @"qq", nil];        NSLog(@"%@", mt);        //添加元素        //Inserts a given object at the end of the array.        [mt addObject:@"fff"];        NSLog(@"%@", mt);        //插入元素       // Inserts a given object into the array's contents at a given index.        [mt insertObject:@"ooo" atIndex:2];        NSLog(@"%@", mt);        //数组连接，，，        //Adds the objects contained in another given array to the end of the receiving array’s content.        [mt addObjectsFromArray:mm];        NSLog(@"%@", mt);                //删除元素        [mt removeObjectAtIndex:2];        NSLog(@"%@", mt);                //替换元素        [mt replaceObjectAtIndex:0 withObject:@"ttttt"];        NSLog(@"%@", mt);                //交换两个指定位置对元素        [mt exchangeObjectAtIndex:0 withObjectAtIndex:1];        NSLog(@"%@", mt);        //图书管理//        NSMutableArray *library = [NSMutableArray arrayWithObjects:@"tushu1",@"tushu2", @"tushu3", @"tushu4", nil];//        NSInteger count1 = [library count];//        NSInteger  ddd;//        NSLog(@"1-添加图书2-删除图书3-修改图书4-查找图书5-查看图书");//        scanf("%ld", &ddd);//        if (ddd == 1) {//            [library addObject:@"tushu5"];//            NSLog(@"%@", library);//        }//        if (ddd == 2) {//            [library removeObject:@"tushu3"];//            NSLog(@"%@", library);//        }//        if (ddd == 3) {//            [library setObject:@"tushu0" atIndexedSubscript:0];//            NSLog(@"%@", library);//        }//        if (ddd == 4) {//            NSInteger place = [library indexOfObject:@"tushu3"];//            NSLog(@"%ld", place);//        }//        if (ddd == 5) {//            for (int i = 0; i < count1; i++) {//                NSLog(@"%@",library[i]);//            }//        }                                //正式作业1；        NSString *jiequ = @"20|http://www.baidu.com";        NSString *neww = [jiequ substringFromIndex:3];  //从这个位置开始截取，  截取前面输出后面。        NSLog(@"%@", neww);                NSString *new = [jiequ substringToIndex:2];    //截取到这个位置        NSLog(@"%@", new);        //将文件改写成213        NSString *qing = @"文艺青年";        NSString *a213 = [qing stringByReplacingOccurrencesOfString:@"文艺" withString:@"213"];        NSLog(@"%@", a213);