NSMutableString vs NSMutableArray

main.m

//
//  main.m
//  Time
//
//  Created by 최건우 on 13. 2. 24..
//  Copyright (c) 2013년 최건우. All rights reserved.
//

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        NSUInteger len = 10000000;
        NSMutableArray *items = [NSMutableArray arrayWithCapacity:len];
        for (NSUInteger i = 0; i < len; i++) {
            [items addObject:[NSString stringWithFormat:@"%ld", (unsigned long)i]];
        }
        
        NSTimeInterval s;
        
        // NSMutableString
        NSMutableString *str = [NSMutableString string];
        s = [[NSDate date] timeIntervalSince1970];
        for (NSString *item in items) {
            [str appendString:item];
        }
        NSLog(@"NSMutableString : %f seconds", [[NSDate date] timeIntervalSince1970] - s);
        
        // NSMutableArray
        NSMutableArray* array = [NSMutableArray array];
        s = [[NSDate date] timeIntervalSince1970];
        for (NSString *item in items) {
            [array addObject:item];
        }
        NSString* result = [array componentsJoinedByString:@""];
        NSLog(@"NSMutableArray : %f seconds", [[NSDate date] timeIntervalSince1970] - s);
        
        assert([result isEqualToString:str]);
    }
    return 0;
}

result.md

Result

2013-02-24 01:45:47.483 Time[90294:303] NSMutableString : 1.177084 seconds
2013-02-24 01:45:49.632 Time[90294:303] NSMutableArray : 2.146141 seconds