直接上代码：* argv[]) {//NSString 类/** 学习系统类需要把握一下几点：* 1、根据给定的初始化方法和便利构造器方法创建对象；* 2、根据需求使用实例方法完成对应的操作；* 3、学会看系统类的头文件；* 4、学会通过帮助文档来学习对应的方法。*/*str1 = @”name” ;NSLog( @”%@”, str1 ) ;// NSString *str2 = [NSString stringWithString:@”name”] ;NSString *str2 = @”name” ;NSLog( @”%@”, str2 ) ;char *cStr = “haha” ;//将C语言字符串转成OC的对象NSString *str3 = [[NSString alloc] initWithCString:cStr encoding:NSUTF8StringEncoding] ;NSLog( @”%@”, str3 ) ;NSString *str4 = [NSString stringWithCString:cStr encoding:NSUTF8StringEncoding] ;NSLog( @”%@”, str4 ) ;//根据指定格式创建字符串NSString *str5 = [[NSString alloc] initWithFormat:@”%@+%d”, @”en”, 1001] ;NSLog( @”%@”, str5 ) ;NSString *str6 = [NSString stringWithFormat:@”%@+%d”, @”ne”, 10014] ;NSLog( @”%@”, str6 ) ;//根据指定路径的文件内容创建字符串对象NSString *str7 = [[NSString alloc] initWithContentsOfFile:@”/Users/lanouhn/Desktop/test.txt” encoding:NSUTF8StringEncoding error:nil] ;NSLog( @”%@”, str7 ) ;// NSError *err = [NSError init] ;NSString *str8 = [NSString stringWithContentsOfFile:@”/Users/lanouhn/Desktop/words.txt” encoding:NSUTF8StringEncoding error:nil] ;NSLog( @”%@”, str8 ) ;//求字符串对象的长度NSInteger length = [str8 length] ;NSLog( @”%ld”, length ) ;//判断一个字符串对象是否拥有前缀字符串BOOL result1 = [str8 hasPrefix:@”If”] ;NSLog( @”%@”, result1 ? @”YES” : @”NO” ) ;//判断一个字符串对象是否拥有后缀BOOL result2 = [str8 hasSuffix:@”en”] ;NSLog( @”%@”, result2 ? @”YES” : @”NO” ) ;//判断一个字符串对象是否和另一个字符串对象相同BOOL result3 = [str8 isEqualToString:str7] ;NSLog( @”%@”, result3 ? @”YES” : @”NO” ) ;NSLog( @”%d”, result3 ) ;//字符串比较排序结果NSComparisonResult result4 = [str8 compare:str7] ;NSLog( @”%ld”, result4 ) ;*subStr1 = [str8 substringFromIndex:1] ;NSLog( @”%@”, subStr1 ) ;//从下标为0的字符开始到指定的下标结束 ，此范围内的字符串NSString *subStr2 = [str8 substringToIndex:2] ;NSLog( @”%@”, subStr2 ) ;//NSRange 为结构体类型， 成员location描述下标位置，，成员length描述需要截取的字符串长度NSRange rang = NSMakeRange(1, 3) ;*subStr3 = [str8 substringWithRange:rang] ;NSLog( @”%@”, subStr3 ) ;*newString1 = [str8 stringByAppendingString:@”+100″] ;NSLog( @”%@”, newString1 ) ;//根据给定的格式串以及参数拼接产生新的字符串NSString *newString2 = [str8 stringByAppendingFormat:@”%d”, 1001] ;NSLog( @”%@”, newString2 ) ;//路径拼接NSString *newString3 = [str8 stringByAppendingPathComponent:@”xx.avi”] ;NSLog( @”%@”, newString3 ) ;*newString4 = [str8 stringByReplacingOccurrencesOfString:@”e” withString:@”呵呵”] ;NSLog( @”%@”, newString4 ) ;//字符串与数值类型数据的转换NSString *numString1 = @”1″ ;NSInteger integerValue = [numString1 integerValue] ;NSLog( @”%ld”, integerValue ) ;float integerValue1 = [numString1 floatValue] ;NSLog( @”%f”, integerValue1 ) ;//大小写转换NSString *string = @” i love you” ;//转成大写字符NSString *upperCaseStr = [string uppercaseString] ;NSLog( @”%@”, upperCaseStr ) ;//转成小写字符NSString *lowercaseStr = [upperCaseStr lowercaseString] ;NSLog( @”%@”, lowercaseStr ) ;//转成首字母大写字符串(每个字符串的首字母转成大写的)NSString *capitalString = [string capitalizedString] ;NSLog( @”%@”, capitalString ) ;/** 可变字符串** NSMutableString**/NSMutableString *mutableStr1 = [[NSMutableString alloc] init] ;NSLog( @”%@”, mutableStr1 ) ;NSMutableString *mutableStr2 = [NSMutableString string] ;//可变字符串的拼接[mutableStr1 appendString:@”abcdef”] ;NSLog( @”%@”, mutableStr1 ) ;NSString *resultString = [mutableStr1 stringByAppendingString:@”xxxx”] ;NSLog( @”%@”, resultString ) ;NSLog( @”%@”, mutableStr1 ) ;//另一个字符串拼接方法//stringByAppendingFormat : appendFormat[mutableStr2 appendFormat:@”wang+%d”, 1001] ;NSLog( @”%@”, mutableStr2 ) ;//删除字符串[mutableStr2 deleteCharactersInRange:NSMakeRange(2, 4)] ;NSLog( @”%@”, mutableStr2 ) ;//插入字符串//在给定的下标之前插入指定的字符串（前插）[mutableStr2 insertString:@”123″ atIndex:2] ;NSLog( @”%@”, mutableStr2 ) ;//替换字符串//根据给定的字符串的替换指定范围的字符们[mutableStr2 replaceCharactersInRange:NSMakeRange(0, 3) withString:@”xxx”] ;NSLog( @”%@”, mutableStr2 ) ;/** 练习一:** 给定一个图片文件名,判断字符串中是否以* “png”结尾,如果是就替换成“jpg”,如果 不是,就拼接”.jpg”。*///不可变 字符串NSString *practiceStr = @”wang/zhen/gang/.png” ;if ( [practiceStr hasSuffix:@”png”] ) {NSLog( @”%@”, [practiceStr stringByReplacingOccurrencesOfString:@”png” withString:@”jpg”] ) ;}else {NSLog( @”%@”, [practiceStr stringByAppendingString:@”.jpg”] ) ;}//可变 字符串NSMutableString *practiceMutableStr = [[NSMutableString alloc] initWithString:@”wang.png”] ;// [practiceMutableStr appendString:@”wang.png”] ; // 注意 NSMutableSring 的初始化 不能用 语法糖if ( [practiceMutableStr hasSuffix:@”png”] ) {//NSLog( @”%@”, [practiceMutableStr stringByReplacingOccurrencesOfString:@”png” withString:@”jpg”]) ;[practiceMutableStr replaceCharactersInRange:[practiceMutableStr rangeOfString:@”png”] withString:@”jpg”] ;}else {[practiceMutableStr appendString:@”.jpg”] ;}NSLog( @”%@”, practiceMutableStr ) ;return 0;}
他们不计后果的彼此拥抱，握紧双手，怕天会亮，怕爱会走。
