OC-NSString从文件中读取字符串

void test2(){    NSString *path = @"/Users/gx/Desktop/test_utf8.txt";    //NSString *str = [NSString stringWithContentsOfFile:path];    //UTF-8编码    NSString *str = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];    NSLog(@"%@",str);        //GBK编码    NSString *path2 = @"/Users/gx/Desktop/test_gbk.txt";    NSString *str2 = [NSString stringWithContentsOfFile:path2 encoding:CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000) error:nil];    NSLog(@"%@",str2);            //使用NSURL从文件中读取字符串    NSURL *url = [NSURL URLWithString:@"file:///Users/gx/Desktop/test_utf8.txt"];    NSString *str3 = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];    NSLog(@"%@",str3);        //使用NSURL读取远程文本    NSURL *url2 = [NSURL URLWithString:@"http://www.baidu.com"];    NSString *str4 = [NSString stringWithContentsOfURL:url2 encoding:NSUTF8StringEncoding error:nil];    NSLog(@"%@",str4);}