new string과 그냥 string

http://hashcode.co.kr/questions/857/%EC%9E%90%EB%B0%94%EC%97%90%EC%84%9C-string%EA%B0%9D%EC%B2%B4%EC%99%80-%EB%AC%B8%EC%9E%90%EC%97%B4-string%EC%9D%98-%EC%B0%A8%EC%9D%B4%EA%B0%80-%EB%AD%94%EA%B0%80%EC%9A%94