25. JAVA Buffer

package basic.exam05.step01;

import java.io.BufferedInputStream;

/* BufferedInputStream/buggeredOutputStream

 * - 파일을 읽을 때 1 바이트씩 읽는 것 보다 왕창 읽는 것이 더 빠르다.

 * - 파일 읽기 시간 = data seek time + data transfer time

 * => data seek time: HDD 해더를 움직여 데이터가 있는 트랙으로 이동한 후

 *                                                          트랙이 돌 때 섹터를 찾는 것 까지의 시간

 * 예 ) 1byte 읽는데 걸리는 시간 = data seek time(예: 0.0085초)

 *                                                + data transfer time(예: 0.000000003초)

 */

public class Episode06 {

       public static void main( String[] args) throws Exception {

             // BufferedInputStream 의 사용 + buf 사용

             FileInputStream in = new FileInputStream("D:/javaide/eclipse-jee-kepler-SR1-win32.zip" );

             BufferedInputStream in2 = new BufferedInputStream(in);

            

             byte[] buf = new byte[ 1024];

             int len = 0;       // 읽어들인 바이트 수

             int b;

             int count = 0;

             long startTime = System .currentTimeMillis();

             while((b = in2 .read(buf )) != -1 ){

                   if((++ count % 10000) == 0){

                         System. out.print( ".");

                         count = 0;

                  }

            }

             long duration = System .currentTimeMillis() - startTime;

             System. out.println( "경과된 시간(밀리초) =" + duration );

            

             in2.close();

             in.close();

      }

       public static void main05( String[] args) throws Exception {

             // BufferedInputStream 의 사용

             FileInputStream in = new FileInputStream("D:/javaide/eclipse-jee-kepler-SR1-win32.zip" );

             BufferedInputStream in2 = new BufferedInputStream(in);

            

             int b;

             int count = 0;

             long startTime = System .currentTimeMillis();

             while((b = in .read()) != -1){

                   if((++ count % 1000000) == 0){

                         System. out.print( ".");

                         count = 0;

                  }

            }

             long duration = System .currentTimeMillis() - startTime;

             System. out.println( "경과된 시간(밀리초) =" + duration );

            

             in2.close();

             in.close();

      }

       public static void main04( String[] args) throws Exception {

             // 8192바이트씩 데이터 읽기

             FileInputStream in = new FileInputStream("D:/javaide/eclipse-jee-kepler-SR1-win32.zip" );

             byte[] buf = new byte[ 8192];  // 보통 버퍼의 크기를 1024 ~ 8192 정도로 설정

             int len = 0;

             int count = 0;

             long startTime = System .currentTimeMillis();

             while((len = in .read(buf )) != -1 ){

                   if((++ count % 100) == 0){

                         System. out.print( ".");

                         count = 0;

                  }

            }

             long duration = System .currentTimeMillis() - startTime;

             System. out.println( "경과된 시간(밀리초) =" + duration );

             in.close();

      }

       public static void main03( String[] args) throws Exception {

             // 1바이트씩 데이터 읽기

             FileInputStream in = new FileInputStream("D:/javaide/eclipse-jee-kepler-SR1-win32.zip" );

             int b;

             int count = 0;

             long startTime = System .currentTimeMillis();

             while((b = in .read()) != -1){

                   if((++ count % 1000000) == 0){

                         System. out.print( ".");

                         count = 0;

                  }

            }

             long duration = System .currentTimeMillis() - startTime;

             System. out.println( "경과된 시간(밀리초) =" + duration );

             in.close();

      }

      

      

       public static void main02( String[] args) throws Exception {

             // 데이터 읽기

             FileInputStream in = new FileInputStream("student3.dat");

             DataInputStream in2 = new DataInputStream(in);

            

             String name = in2.readUTF();

             int kor = in2.readInt();

             int eng = in2.readInt();

             int math = in2.readInt();

             int sum = in2.readInt();

            

             System. out.println( name);

             System. out.println( kor);

             System. out.println( eng);

             System. out.println( math);

             System. out.println( sum);

            

             in2.close();

             in.close();

      }

      

      

       public static void main01( String[] args) throws Exception {

             // 데이터 출력

             FileOutputStream out = new FileOutputStream("student3.dat" );

             DataOutputStream out2 = new DataOutputStream(out);

            

             String name = "홍길동";

             int kor = 90, eng = 100, math = 80, sum = 270;

             out2.writeUTF( name);    

             out2.writeInt( kor);                 

             out2.writeInt( eng);                 

             out2.writeInt( math);    

             out2.writeInt( sum);           

            

             out2.close();

             out.close();

      }

}