Objective-C string class, array class

String class ：

        NSString* str1 = @"dancer";
        NSString* str2 = [[NSString alloc] initWithFormat:@"%d beijing",1949];
        NSString* str3 = [NSString stringWithFormat:@"%ld beijing",1948];
        NSUInteger len = str1.length;
        // Calculate the length 
        // notes ： One Chinese character and one length 
        NSLog(@"%lu",len);
        // More equal 
        BOOL result = [str1 isEqualTo:str2];
        if(result){
            NSLog(@" equal ");
        }else{
            NSLog(@" It's not equal ");
        }

Array class ：

        //NSMutableArray Variable array 
        NSMutableArray* array = [[NSMutableArray alloc]init];
        // Arrays can hold objects of any type 
        // Additions and deletions 
        [array addObject:@"obj1"];
        // Delete by object 
        [array removeObject:@"obj1"];
        // Delete... By index 
        [array removeObjectAtIndex:0];
        // Accessing array elements 
        NSString* item1 =  array[0];