diff -r cdfc278e37b9 -r 6512884e03b4 progs/catastrophic.java --- a/progs/catastrophic.java Mon Jul 27 01:55:05 2020 +0100 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,45 +0,0 @@ -// A case of catastrophic backtracking in Java 8 -//----------------------------------------------- -// -// regexp: (a*)*b -// strings: aa.... -// -// compile: javac catastrophic.java -// call with: java catastrophic -// -// IMPORTANT: -// Java 9 improved its regex matching engine. -// This example is now much faster. -// - -import java.util.regex.*; - -public class catastrophic { - public static void main(String[] args) { - - //we always run all the tests twice -> to warmup of the JVM - for (int runs = 0; runs < 2; runs++) { - - Pattern pattern = Pattern.compile("(a*)*b"); - - // Run from 5 to 28 characters - for (int length = 5; length < 28; length++) { - - // Build input of specified length - String input = ""; - for (int i = 0; i < length; i++) { input += "a"; } - - // Measure the average duration of two calls... - long start = System.nanoTime(); - for (int i = 0; i < 2; i++) { - pattern.matcher(input).find(); - } - - // Print out time - System.out.println(length + " " + input + ": " - + ((System.nanoTime() - start) / 2000000000d) - + "s"); - } - } - } -}