Name: jl125535 Date: 06/23/2004


FULL PRODUCT VERSION :
java version "1.5.0-beta3"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta3-b56)
Java HotSpot(TM) Client VM (build 1.5.0-beta3-b56, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
The code to sum a column of Integers (400 000) using java.util.Scanner
is 10 times slower than it's JDK1.4 counterpart
(with BufferedReader.readLine() and Integer.parseInt()).

I think this performance problem is a serious handicap to
the scanner adoption.

I see at least one optimisation.
It is not necessary to create an intermediary string,
the code of Integer.parseInt() could be written using
a CharSequence.




STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
generate a text file
C:\eclipse\workspace\bits>java -cp classes15 LineGenerator > test.txt

run the two programms :
C:\eclipse\workspace\bits>java -cp classes15 AddLine2 < test.txt
C:\eclipse\workspace\bits>java -cp classes15 AddLine < test.txt

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
>java -cp classes15 AddLine2 < test.txt
-1604578624
(a number near 343108971)

>java -cp classes15 AddLine < test.txt
-1604578624
343108971

ACTUAL -
>java -cp classes15 AddLine2 < test.txt
-1604578624
3192452393

>java -cp classes15 AddLine < test.txt
-1604578624
343108971

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
AddLine:
import java.io.*;
import java.util.*;

public class AddLine {
  public static void main(String[] args) throws IOException{
    long time=System.nanoTime();
    
    int sum = 0;
    String line;
    
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    while ((line = in.readLine()) != null) {
      sum = sum + Integer.parseInt(line);
    }
    System.out.println(sum);
    
    System.out.println(System.nanoTime()-time);
  }
}


AddLine2:
import java.util.*;

public class AddLine2 {
  public static void main(String[] args) {
    long time=System.nanoTime();
   
    int sum = 0;
    Scanner scanner=new Scanner(System.in);
    while (scanner.hasNextInt()) {
      sum = sum + scanner.nextInt();
    }
    System.out.println(sum);
    
    System.out.println(System.nanoTime()-time);
  }
}


LineGenerator:
public class LineGenerator {
  public static void main(String[] args) {
    for(int i=0;i<400000;i++)
      System.out.println(i);
  }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
don't use java.util.Scanner
(Incident Review ID: 280992)
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