diff -r 000000000000 -r fb9019fb1bf7 src/net/fortuna/ical4j/util/UidGenerator.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/net/fortuna/ical4j/util/UidGenerator.java	Tue Feb 10 18:12:00 2015 +0100
@@ -0,0 +1,109 @@
+/**
+ * Copyright (c) 2012, Ben Fortuna
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *  o Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ *  o Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ *  o Neither the name of Ben Fortuna nor the names of any other contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package net.fortuna.ical4j.util;
+
+import java.net.SocketException;
+
+import net.fortuna.ical4j.model.DateTime;
+import net.fortuna.ical4j.model.property.Uid;
+
+/**
+ * $Id$
+ *
+ * Created on 11/03/2007
+ *
+ * Generates {@link Uid} properties in a similar fashion to that recommended in section 4.8.4.7 of the specification.
+ * @author Ben Fortuna
+ */
+public class UidGenerator {
+
+    private final String pid;
+
+    private final HostInfo hostInfo;
+
+    private static long lastMillis;
+
+    /**
+     * @param pid a unique process identifier for the host machine
+     * @throws SocketException where host information cannot be retrieved
+     */
+    public UidGenerator(String pid) throws SocketException {
+        this(new InetAddressHostInfo(), pid);
+    }
+
+    /**
+     * @param hostInfo custom host information
+     * @param pid a unique process identifier for the host machine
+     */
+    public UidGenerator(HostInfo hostInfo, String pid) {
+        this.hostInfo = hostInfo;
+        this.pid = pid;
+    }
+
+    /**
+     * @return a unique component identifier
+     */
+    public Uid generateUid() {
+        final StringBuffer b = new StringBuffer();
+        b.append(uniqueTimestamp());
+        b.append('-');
+        b.append(pid);
+        if (hostInfo != null) {
+            b.append('@');
+            b.append(hostInfo.getHostName());
+        }
+        return new Uid(b.toString());
+    }
+
+    /**
+     * Generates a timestamp guaranteed to be unique for the current JVM instance.
+     * @return a {@link DateTime} instance representing a unique timestamp
+     */
+    private static DateTime uniqueTimestamp() {
+        long currentMillis;
+        synchronized (UidGenerator.class) {
+            currentMillis = System.currentTimeMillis();
+            // guarantee uniqueness by ensuring timestamp is always greater
+            // than the previous..
+            if (currentMillis < lastMillis) {
+                currentMillis = lastMillis;
+            }
+            if (currentMillis - lastMillis < Dates.MILLIS_PER_SECOND) {
+                currentMillis += Dates.MILLIS_PER_SECOND;
+            }
+            lastMillis = currentMillis;
+        }
+        final DateTime timestamp = new DateTime(currentMillis);
+        timestamp.setUtc(true);
+        return timestamp;
+    }
+}