diff --git a/regex/RegexDemo.java b/regex/RegexDemo.java
new file mode 100644
index 0000000..acfcde5
--- /dev/null
+++ b/regex/RegexDemo.java
@@ -0,0 +1,41 @@
+import java.util.regex.Pattern;
+import java.util.regex.Matcher;
+
+public class RegexDemo {
+    public static void simpleDemo() {
+        String s1 = "moons";
+        String s2 = "XxmoonsxX";
+        String regexString = "m[aeiou]{2}ns";
+        System.out.println(s1.matches(regexString));
+        System.out.println(s2.matches(regexString));
+    }
+
+    public static void matcherDemo() {
+        String seq = "GPCGGWCAASCGGPYACGGWAGYHAGWHWAH";
+        String regexString = "C.{2,4}C.{3}[LIVMFYWCX].{8}H.{3,5}H";
+        Pattern pat = Pattern.compile(regexString);
+
+        Matcher mat = pat.matcher(seq);
+        while (mat.find()) {
+            System.out.println("Match: " + mat.group(0));
+        }
+    }
+
+    public static void groupDemo() {
+        String seq = "jim,cs61b-abe,30117827,xi,cs61b-bqd,15039872";
+        String regexString = "(cs61b-[a-z]{3}),([0-9]+)";
+        Pattern pat = Pattern.compile(regexString);
+        Matcher mat = pat.matcher(seq);
+        while (mat.find()) {
+            System.out.println("entire match: " + mat.group(0));
+            System.out.println("login: " + mat.group(1) + ", sid: "
+                    + mat.group(2));
+        }
+    }
+
+    public static void main(String[] args) {
+        //simpleDemo();
+        //matcherDemo();
+        //groupDemo();
+    }
+}