From 01e57c998e0bdde8e65b07cc07bc6facf49014ff Mon Sep 17 00:00:00 2001
From: HoaPhan <s50600822@gmail.com>
Date: Wed, 8 Nov 2023 12:04:58 +1100
Subject: [PATCH] JDK 8 11 17 21 regexp perf

---
 vs/java/regexp/Readme.md | 50 ++++++++++++++++++++++++++++++++++++++++
 vs/java/regexp/Reg.java  | 28 ++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100644 vs/java/regexp/Readme.md
 create mode 100644 vs/java/regexp/Reg.java

diff --git a/vs/java/regexp/Readme.md b/vs/java/regexp/Readme.md
new file mode 100644
index 00000000..cabc7675
--- /dev/null
+++ b/vs/java/regexp/Readme.md
@@ -0,0 +1,50 @@
+
+### 8.332.08.1-amzn, java 11.0.16-amzn, java 17.0.8-amzn, java 21-graalce
+```
+sdk use java 8.332.08.1-amzn
+javac Reg.java && java Reg
+time: false [22197 ms]
+
+sdk use java 11.0.16-amzn
+javac Reg.java && java Reg
+time: false [5 ms]
+
+
+sdk use java 17.0.8-amzn
+javac Reg.java && java Reg
+time: false [2 ms]
+
+
+sdk use java 21-graalce
+javac Reg.java && java Reg
+time: false [0 ms]
+
+```
+
+### 21 Amaz vs 21 Graal native (nanosec scale)
+
+```
+Using java version 21-amzn in this shell.
+[2295042 ns]
+[2043833 ns]
+[2035208 ns]
+[2039458 ns]
+[2123292 ns]
+[2206541 ns]
+
+graalvm native
+[115458 ns]
+[140333 ns]
+[101666 ns]
+[122791 ns]
+[116959 ns]
+[177125 ns]
+[119584 ns]
+```
+
+### ref
+https://kean.blog/post/regex-matcher
+https://kean.blog/post/regex-matcher
+https://algs4.cs.princeton.edu/54regexp/
+https://querix.com/go/lycia/Content/06_reference/4gl/regular_expressions/regex_algorithms.htm
+https://sedgewick.io/wp-content/uploads/2022/04/Algs20-RegularExpressions.pdf
\ No newline at end of file
diff --git a/vs/java/regexp/Reg.java b/vs/java/regexp/Reg.java
new file mode 100644
index 00000000..e28871de
--- /dev/null
+++ b/vs/java/regexp/Reg.java
@@ -0,0 +1,28 @@
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class Reg {
+
+    public static void main(String[] args) {
+        long startTime = System.nanoTime();
+        boolean m = reg();
+        long endTime = System.nanoTime();
+        long durationMs = (endTime - startTime)/1000000;
+
+        System.out.println(String.format("time: %s [%s ms]" , m ,durationMs));
+    }
+
+    public static String reverseString(String str) {
+        if (str.isEmpty())
+            return str;
+        return reverseString(str.substring(1)) + str.charAt(0);
+    }
+
+    public static boolean reg(){
+        final String expr = "(a|b|ab)*bc";
+        final String in = "ababababababababababababababababababababababababababababac";
+        Pattern p = Pattern.compile(expr);
+        Matcher m = p.matcher(in);
+        return m.matches();
+    }
+}
\ No newline at end of file