This section provides a tutorial example to test performance of 2 Java built-in functions: substring() and indexOf() on a Window 2000 system.
To compare the performance with Java language, I wrote the following
program, SubstringTest.java, in 2002 with almost identical statement
structure as SubstringTest.pl, using substring() and indexOf():
/**
* SubstringTest.java
* Copyright (c) 2002 by Dr. Herong Yang, http://www.herongyang.com/
*/
import java.util.*;
class SubstringTest {
static int numChar = 10;
static int numTest = 1;
static String baseString = null;
static String subString = null;
static Random randomGenerator = null;
public static void main(String[] a) {
if (a.length>0) numChar = Integer.parseInt(a[0]);
if (a.length>1) numTest = Integer.parseInt(a[1]);
randomGenerator = new Random();
baseString = setString(numChar);
subString = setString(numChar);
long startTime = (new Date()).getTime();
long numMatch = 0;
for (int i=0; i<numTest; i++) {
numMatch = test();
}
long endTime = (new Date()).getTime();
long totalTime = (endTime - startTime)/1000;
long averageTime = totalTime/numTest;
System.out.println("Number of tests = "+numTest);
System.out.println("Number of characters = "+numChar);
System.out.println("Number of matches = "+numMatch);
System.out.println("Total time = "+totalTime+" seconds");
System.out.println("Average time = "+averageTime+" seconds");
}
private static String setString (int size) {
StringBuffer str = new StringBuffer();
for (int i=0; i<size; i++) {
int n = randomGenerator.nextInt(96) + 32;
char c = (char) n;
str.append(c);
}
return str.toString();
}
private static long test() {
int i,j,l;
String str = null;
int num = 0;
int pos = -1;
for (i=0; i<numChar; i++) {
l = i+1;
for (j=0; j<numChar-i; j++) {
str = subString.substring(j,j+l);
pos = baseString.indexOf(str);
if (pos<0) num++;
}
}
return num;
}
}
Running it on the sample system, I got the following result:
>\j2sdk1.4.1_01\bin\java -cp . SubstringTest 50 1000
Number of tests = 1000
Number of characters = 50
Number of matches = 1261
Total time = 1 seconds
Average time = 0 seconds
>\j2sdk1.4.1_01\bin\java -cp . SubstringTest 100 1000
Number of tests = 1000
Number of characters = 100
Number of matches = 4986
Total time = 7 seconds
Average time = 0 seconds
>\j2sdk1.4.1_01\bin\java -cp . SubstringTest 200 1000
Number of tests = 1000
Number of characters = 200
Number of matches = 19933
Total time = 56 seconds
Average time = 0 seconds
Conclusion: Java is much more efficient than Perl with sub string
and string match functions.
