better formatting for execution times

- now using default Guava Stopwatch formatting when calculating
execution times for several operations

src/main/java/org/codarama/diet/api/reporting/MinimizationStatistics.java

@@ -7,9 +7,9 @@
 public interface MinimizationStatistics {
 
 	/**
-	 * @return the total time it took to finish the minimization process (in milliseconds)
+	 * @return a formatted message telling the total time it took to finish the minimization process
 	 */
-	long getTotalExecutionTime();
+	String getFormattedExecutionTime();
 
 	/**
 	 * @return the number of sources that were considered by the minimization engine

src/main/java/org/codarama/diet/api/reporting/ReportBuilder.java

@@ -5,6 +5,7 @@
 import java.util.Set;
 import java.util.jar.JarFile;
 
+import com.google.common.base.Stopwatch;
 import org.codarama.diet.model.ClassFile;
 import org.codarama.diet.model.SourceFile;
 
@@ -13,11 +14,11 @@
  */
 public class ReportBuilder {
 
-	private long startTime;
-
 	private MinimizationStatisticsImplementation statistics = new MinimizationStatisticsImplementation();
 	private MinimizationReportImplementation report = new MinimizationReportImplementation(statistics);
 
+	private Stopwatch stopwatch;
+
 	private ReportBuilder() {
 		// Disable class instantiation from other classes
 	}
@@ -30,7 +31,7 @@ private ReportBuilder() {
 	 */
 	public static ReportBuilder startClock() {
 		ReportBuilder builder = new ReportBuilder();
-		builder.startTime = System.currentTimeMillis();
+		builder.stopwatch = Stopwatch.createStarted();
 		return builder;
 	}
 
@@ -101,8 +102,8 @@ public ReportBuilder minimizedLibs(Set<?> foundDependencies) {
 	 * @return the instance of the {@link ReportBuilder} for chaining purposes
 	 */
 	public ReportBuilder stopClock() {
-		long endTime = System.currentTimeMillis();
-		this.statistics.totalTime = endTime - startTime;
+		this.stopwatch.stop();
+		this.statistics.totalTimeMsg = stopwatch.toString();
 
 		return this;
 	}
@@ -139,11 +140,11 @@ private class MinimizationStatisticsImplementation implements MinimizationStatis
 		private int minimizedDependenciesCount;
 		private int totalDependenciesCount;
 		private int sourcesCount;
-		private long totalTime;
+		private String totalTimeMsg;
 
 		@Override
-		public long getTotalExecutionTime() {
-			return this.totalTime;
+		public String getFormattedExecutionTime() {
+			return this.totalTimeMsg;
 		}
 
 		@Override

src/main/java/org/codarama/diet/dependency/resolver/impl/ClassStreamDependencyResolver.java

@@ -50,7 +50,7 @@ public Set<ClassName> resolve(ClassStream classStream) throws IOException {
         stopwatch.stop();
         eventBus.post(
                 new ClassDependencyResolutionEndEvent("Class dependency resolution took: "
-                        + stopwatch.elapsed(TimeUnit.SECONDS), this.getClass())
+                        + stopwatch.toString(), this.getClass())
         );
 
         return result;

src/test/java/org/codarama/diet/api/MinimizerUnitTest.java

@@ -4,15 +4,13 @@
 import static org.junit.Assert.*;
 
 import java.io.IOException;
-import java.util.Iterator;
 import java.util.Set;
 import java.util.jar.JarFile;
 
 import org.codarama.diet.api.reporting.MinimizationReport;
 import org.codarama.diet.api.reporting.MinimizationStatistics;
 import org.codarama.diet.model.ClassName;
 import org.junit.Before;
-import org.junit.Test;
 
 /**
  * Unit tests for the {@link DefaultMinimizer}.
@@ -32,7 +30,7 @@ public void init() throws IOException {
       when(mockStatistics.getMinimizedDependenciesCount()).thenReturn(10);
       when(mockStatistics.getSourceFilesCount()).thenReturn(200);
       when(mockStatistics.getTotalDependenciesCount()).thenReturn(1000);
-      when(mockStatistics.getTotalExecutionTime()).thenReturn(5L * 60L * 1000L);
+      when(mockStatistics.getFormattedExecutionTime()).thenReturn(String.valueOf(5L * 60L * 1000L));
 
       final JarFile minimizationResult = mock(JarFile.class);
       when(minimizationResult.getName()).thenReturn("diet.jar");