--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/catastrophic/catastrophic.java	Mon Jul 27 11:02:48 2020 +0100
@@ -0,0 +1,45 @@
+// 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");
+            }
+        }
+    }
+}