[Java] String과 StringBuffer의 속도 차이

*. 테스트 소스

class aa {   
 public static void main(String[] args) {
  String aa =   "aa      \n"
              + "bb      \n"
              + "cc      \n";
             
        System.out.println(aa);
 
  StringBuffer bb = new StringBuffer();
  bb.append("  aa      \n");
  bb.append("  bb      \n");
  bb.append("  xx      \n");
 
  System.out.println(bb.toString());
 
  StringBuffer cc = new StringBuffer()
  .append("  aaa      \n")
  .append("  bbb      \n")
  .append("  ccc      \n");
 
  System.out.println(cc.toString());

 }
   
}

*. 디어셈블 결과

C:\j2sdk1.4.2_12\bin>javap -c aa
Compiled from "aa.java"
class aa extends java.lang.Object{
aa();
  Code:
   0:   aload_0
   1:   invokespecial   #1; //Method java/lang/Object."<init>":()V
   4:   return

public static void main(java.lang.String[]);
  Code:
   0:   ldc     #2; //String aa      \nbb      \ncc      \n                        
   2:   astore_1
   3:   getstatic       #3; //Field java/lang/System.out:Ljava/io/PrintStream;
   6:   aload_1
   7:   invokevirtual   #4; //Method java/io/PrintStream.println:(Ljava/lang/Str
ing;)V
   10:  new     #5; //class StringBuffer
   13:  dup
   14:  invokespecial   #6; //Method java/lang/StringBuffer."<init>":()V
   17:  astore_2
   18:  aload_2
   19:  ldc     #7; //String   aa      \n
   21:  invokevirtual   #8; //Method java/lang/StringBuffer.append:(Ljava/lang/S
tring;)Ljava/lang/StringBuffer;
   24:  pop
   25:  aload_2
   26:  ldc     #9; //String   bb      \n
   28:  invokevirtual   #8; //Method java/lang/StringBuffer.append:(Ljava/lang/S
tring;)Ljava/lang/StringBuffer;
   31:  pop
   32:  aload_2
   33:  ldc     #10; //String   xx      \n
   35:  invokevirtual   #8; //Method java/lang/StringBuffer.append:(Ljava/lang/S
tring;)Ljava/lang/StringBuffer;
   38:  pop
   39:  getstatic       #3; //Field java/lang/System.out:Ljava/io/PrintStream;
   42:  aload_2
   43:  invokevirtual   #11; //Method java/lang/StringBuffer.toString:()Ljava/la
ng/String;
   46:  invokevirtual   #4; //Method java/io/PrintStream.println:(Ljava/lang/Str
ing;)V
   49:  new     #5; //class StringBuffer
   52:  dup
   53:  invokespecial   #6; //Method java/lang/StringBuffer."<init>":()V
   56:  ldc     #12; //String   aaa      \n
   58:  invokevirtual   #8; //Method java/lang/StringBuffer.append:(Ljava/lang/S
tring;)Ljava/lang/StringBuffer;
   61:  ldc     #13; //String   bbb      \n
   63:  invokevirtual   #8; //Method java/lang/StringBuffer.append:(Ljava/lang/S
tring;)Ljava/lang/StringBuffer;
   66:  ldc     #14; //String   ccc      \n
   68:  invokevirtual   #8; //Method java/lang/StringBuffer.append:(Ljava/lang/S
tring;)Ljava/lang/StringBuffer;
   71:  astore_3
   72:  getstatic       #3; //Field java/lang/System.out:Ljava/io/PrintStream;
   75:  aload_3
   76:  invokevirtual   #11; //Method java/lang/StringBuffer.toString:()Ljava/la
ng/String;
   79:  invokevirtual   #4; //Method java/io/PrintStream.println:(Ljava/lang/Str
ing;)V
   82:  return

}

위 결과에서 볼 수 있듯이 StringBuffer보다 String이 속도가 더 빠르다는 것을 알 수 있다.
뭐가 좋고 나쁨을 말할순 없지만 상황에따라 잘 사용 해야 할것 같다.

참고.

     1. String aa =   "aa      \n"
              + "bb      \n"
              + "cc      \n";
             
     2. String aa  = "aa      \n";
         aa += "bb      \n";
         aa += "cc      \n";
        
1번과 2번의 결과는 다르다는 것을 알고 있어야 한다.
2번 같은 경우는 StringBuffer와 같이 서로 다른 라인으로 인식하여 실행되기 때문이다.