Index: trunk/java-utils/src/main/java/de/ugoe/cs/util/StopWatch.java
===================================================================
--- trunk/java-utils/src/main/java/de/ugoe/cs/util/StopWatch.java	(revision 1128)
+++ trunk/java-utils/src/main/java/de/ugoe/cs/util/StopWatch.java	(revision 1128)
@@ -0,0 +1,315 @@
+//   Copyright 2012 Georg-August-Universität Göttingen, Germany
+//
+//   Licensed under the Apache License, Version 2.0 (the "License");
+//   you may not use this file except in compliance with the License.
+//   You may obtain a copy of the License at
+//
+//       http://www.apache.org/licenses/LICENSE-2.0
+//
+//   Unless required by applicable law or agreed to in writing, software
+//   distributed under the License is distributed on an "AS IS" BASIS,
+//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//   See the License for the specific language governing permissions and
+//   limitations under the License.
+
+package de.ugoe.cs.util;
+
+import java.io.PrintStream;
+import java.text.DecimalFormat;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * <p>
+ * This is a simple implementation for a stop watch that can be used for performance measures.
+ * A stop watch can be used to measure several splits. Each split is started and stopped using the
+ * same id provided to the {@link #start(String)} and {@link #stop(String)} methods. The measured
+ * durations can be retrieved afterwards using {@link #getDuration(String)}.
+ * {@link #dumpStatistics(PrintStream)} is a convenience method useful to effectively dump all
+ * information for the different splits.
+ * </p>
+ * 
+ * @author Patrick Harms
+ */
+public class StopWatch {
+    
+    /**
+     * the splits hold internally
+     */
+    private Map<String, Split> mSplits = new HashMap<String, Split>();
+
+    /**
+     * starts a split with the given id. If the split with the id is already started, an
+     * {@link IllegalStateException} is thrown.
+     *
+     * @param id the id of the split to be started
+     * 
+     * @throws IllegalStateException if the split is already started
+     */
+    public void start(String id) throws IllegalStateException {
+        Split split = mSplits.get(id);
+        
+        if (split == null) {
+            split = new Split(id);
+            mSplits.put(id, split);
+        }
+        
+        split.start();
+    }
+    
+    /**
+     * stops a split with the given id. If the split with the id is already stopped, an
+     * {@link IllegalStateException} is thrown. If no split with the given id exists, an
+     * {@link IllegalArgumentException} is thrown.
+     *
+     * @param id the id of the split to be stopped
+     * 
+     * @throws IllegalStateException    if the split is not running
+     * @throws IllegalArgumentException if the split with the given id does not exist
+     */
+    public void stop(String id) throws IllegalStateException, IllegalArgumentException {
+        Split split = mSplits.get(id);
+       
+        if (split == null) {
+            throw new IllegalArgumentException("split with id " + id + " does not exist");
+        }
+       
+        split.stop();
+    }
+    
+    /**
+     * returns the duration of a split with the given id. If the split with the id is currently
+     * running, it is stopped. If no split with the given id exists, an
+     * {@link IllegalArgumentException} is thrown.
+     *
+     * @param id the id of the split for which the duration shall be returned
+     * 
+     * @return the duration measured for the split
+     * 
+     * @throws IllegalArgumentException if the split with the given id does not exist
+     */
+    public long getDuration(String id) throws IllegalArgumentException {
+        Split split = mSplits.get(id);
+        
+        if (split == null) {
+            throw new IllegalArgumentException("split with id " + id + " does not exist");
+        }
+       
+        if (split.isRunning()) {
+            split.stop();
+        }
+        
+        return split.getDuration();
+    }
+
+    /**
+     * resets the stop watch and clears all splits 
+     */
+    public void reset() {
+        mSplits.clear();
+    }
+    
+    /**
+     * dumps the statistics about the splits. Splits still running are stopped. The method checks
+     * if the longest split also covers the other splits. If so, it considers this split as a
+     * kind of overall duration and dumps the proportion of all other splits to this split in
+     * percentage.
+     * 
+     * @param out the stream to dump the statistics to
+     */
+    public void dumpStatistics(PrintStream out) {
+        if (mSplits.size() <= 0) {
+            throw new IllegalStateException("no splits registered that could be dumped");
+        }
+        
+        Map<String, Long> durations = new HashMap<String, Long>();
+        
+        // get durations
+        for (String id : mSplits.keySet()) {
+            durations.put(id, getDuration(id));
+        }
+        
+        // sort by duration
+        List<String> sortedIds = new LinkedList<String>();
+        int maxIdLength = 0;
+        
+        for (Map.Entry<String, Long> entry : durations.entrySet()) {
+            boolean added = false;
+            for (int i = 0; i < sortedIds.size(); i++) {
+                if (durations.get(sortedIds.get(i)) >= entry.getValue()) {
+                    sortedIds.add(i, entry.getKey());
+                    added = true;
+                    break;
+                }
+            }
+           
+            if (!added) {
+                sortedIds.add(entry.getKey());
+            }
+            
+            maxIdLength = Math.max(maxIdLength, entry.getKey().length());
+        }
+        
+        // get longest duration and check whether it spans all other entries
+        String id = sortedIds.get(sortedIds.size() - 1);
+        Split longestWatch = mSplits.get(id);
+        boolean longestDurationCoversOthers = true;
+        
+        for (Map.Entry<String, Split> watch : mSplits.entrySet()) {
+            if ((watch.getValue().getFirstStart() < longestWatch.getFirstStart()) ||
+                (watch.getValue().getLastStop() > longestWatch.getLastStop()))
+            {
+                longestDurationCoversOthers = false;
+                break;
+            }
+        }
+        
+        // no finally start the dumping
+        out.println();
+        out.println("Watch Statistics");
+        out.println("================");
+
+        for (String sortedId : sortedIds) {
+            out.print(sortedId);
+            
+            for (int i = sortedId.length(); i <= maxIdLength; i++) {
+                out.print(' ');
+            }
+            
+            out.print(": ");
+            
+            out.print(durations.get(sortedId));
+            out.print(" ms");
+            
+            out.print(" (");
+            out.print(mSplits.get(sortedId).getNoOfStarts());
+            out.print(" starts");
+            
+            //out.print(", ");
+            //out.print(1000 * durations.get(sortedId) / mSplits.get(sortedId).getNoOfStarts());
+            //out.print(" ms per 1000 starts");
+
+            if (longestDurationCoversOthers) {
+                out.print(", ");
+                out.print(DecimalFormat.getPercentInstance().format
+                              ((double) durations.get(sortedId) / longestWatch.getDuration()));
+                out.print(" of overall duration");
+            }
+            
+            out.println(')');
+        }
+        
+        out.println();
+    }
+    
+    /**
+     * internally used to store splits
+     */
+    private static class Split {
+        
+        /**
+         * the id of the split
+         */
+        private String id;
+        
+        /**
+         * the system time of the first start of the split
+         */
+        private long firstStart = -1;
+        
+        /**
+         * the system time of the last start of the split
+         */
+        private long lastStart = -1;
+        
+        /**
+         * the system time of the last stop of the split
+         */
+        private long lastStop = -1;
+        
+        /**
+         * the duration so far for the split (excluding the time since the last start)
+         */
+        private long duration = 0;
+        
+        /**
+         * the number of starts or the splits
+         */
+        private long noOfStarts = 0;
+        
+        /**
+         * initializes the split with its id
+         */
+        private Split(String id) {
+            this.id = id;
+        }
+        
+        /**
+         * starts the split if it is not already started
+         */
+        private void start() throws IllegalStateException {
+            if (lastStart > -1) {
+                throw new IllegalStateException("split with id " + id + " already running");
+            }
+            
+            lastStart = System.currentTimeMillis();
+            
+            if (firstStart < 0) {
+                firstStart = lastStart;
+            }
+            
+            noOfStarts++;
+        }
+        
+        /**
+         * checks if the split is currently running
+         */
+        private boolean isRunning() {
+            return (lastStart > -1);
+        }
+        
+        /**
+         * stops the split if it is not already stopped
+         */
+        private void stop() throws IllegalStateException {
+            if (lastStart < 0) {
+                throw new IllegalStateException("split with id " + id + " not running");
+            }
+            
+            lastStop = System.currentTimeMillis();
+            duration += lastStop - lastStart;
+            lastStart = -1;
+        }
+        
+        /**
+         * returns the fist start of the split
+         */
+        private long getFirstStart() {
+            return firstStart;
+        }
+
+        /**
+         * returns the last stop of the split
+         */
+        private long getLastStop() {
+            return lastStop;
+        }
+
+        /**
+         * returns the duration of the split measured so far excluding the time since the last 
+         * start if the split is currently started
+         */
+        private long getDuration() {
+            return duration;
+        }
+
+        /**
+         * returns the number of starts for the split
+         */
+        private long getNoOfStarts() {
+            return noOfStarts;
+        }
+    }
+}