Simple stop watch : StopWatch « Development Class « Java






Simple stop watch

  
/*
 * Copyright 2002-2007 the original author or authors.
 *
 * 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.
 */


import java.text.NumberFormat;
import java.util.LinkedList;
import java.util.List;

/**
 * Simple stop watch, allowing for timing of a number of tasks,
 * exposing total running time and running time for each named task.
 *
 * <p>Conceals use of <code>System.currentTimeMillis()</code>, improving the
 * readability of application code and reducing the likelihood of calculation errors.
 *
 * <p>Note that this object is not designed to be thread-safe and does not
 * use synchronization.
 *
 * <p>This class is normally used to verify performance during proof-of-concepts
 * and in development, rather than as part of production applications.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since May 2, 2001
 */
public class StopWatch {

  /**
   * Identifier of this stop watch.
   * Handy when we have output from multiple stop watches
   * and need to distinguish between them in log or console output.
   */
  private final String id;

  private boolean keepTaskList = true;

  /** List of TaskInfo objects */
  private final List taskList = new LinkedList();

  /** Start time of the current task */
  private long startTimeMillis;

  /** Is the stop watch currently running? */
  private boolean running;

  /** Name of the current task */
  private String currentTaskName;

  private TaskInfo lastTaskInfo;

  private int taskCount;

  /** Total running time */
  private long totalTimeMillis;


  /**
   * Construct a new stop watch. Does not start any task.
   */
  public StopWatch() {
    this.id = "";
  }

  /**
   * Construct a new stop watch with the given id.
   * Does not start any task.
   * @param id identifier for this stop watch.
   * Handy when we have output from multiple stop watches
   * and need to distinguish between them.
   */
  public StopWatch(String id) {
    this.id = id;
  }

  /**
   * Determine whether the TaskInfo array is built over time. Set this to
   * "false" when using a StopWatch for millions of intervals, or the task
   * info structure will consume excessive memory. Default is "true".
   */
  public void setKeepTaskList(boolean keepTaskList) {
    this.keepTaskList = keepTaskList;
  }


  /**
   * Start an unnamed task. The results are undefined if {@link #stop()}
   * or timing methods are called without invoking this method.
   * @see #stop()
   */
  public void start() throws IllegalStateException {
    start("");
  }

  /**
   * Start a named task. The results are undefined if {@link #stop()}
   * or timing methods are called without invoking this method.
   * @param taskName the name of the task to start
   * @see #stop()
   */
  public void start(String taskName) throws IllegalStateException {
    if (this.running) {
      throw new IllegalStateException("Can't start StopWatch: it's already running");
    }
    this.startTimeMillis = System.currentTimeMillis();
    this.running = true;
    this.currentTaskName = taskName;
  }

  /**
   * Stop the current task. The results are undefined if timing
   * methods are called without invoking at least one pair
   * {@link #start()} / {@link #stop()} methods.
   * @see #start()
   */
  public void stop() throws IllegalStateException {
    if (!this.running) {
      throw new IllegalStateException("Can't stop StopWatch: it's not running");
    }
    long lastTime = System.currentTimeMillis() - this.startTimeMillis;
    this.totalTimeMillis += lastTime;
    this.lastTaskInfo = new TaskInfo(this.currentTaskName, lastTime);
    if (this.keepTaskList) {
      this.taskList.add(lastTaskInfo);
    }
    ++this.taskCount;
    this.running = false;
    this.currentTaskName = null;
  }

  /**
   * Return whether the stop watch is currently running.
   */
  public boolean isRunning() {
    return this.running;
  }


  /**
   * Return the time taken by the last task.
   */
  public long getLastTaskTimeMillis() throws IllegalStateException {
    if (this.lastTaskInfo == null) {
      throw new IllegalStateException("No tests run: can't get last interval");
    }
    return this.lastTaskInfo.getTimeMillis();
  }

  /**
   * Return the total time in milliseconds for all tasks.
   */
  public long getTotalTimeMillis() {
    return totalTimeMillis;
  }

  /**
   * Return the total time in seconds for all tasks.
   */
  public double getTotalTimeSeconds() {
    return totalTimeMillis / 1000.0;
  }

  /**
   * Return the number of tasks timed.
   */
  public int getTaskCount() {
    return taskCount;
  }

  /**
   * Return an array of the data for tasks performed.
   */
  public TaskInfo[] getTaskInfo() {
    if (!this.keepTaskList) {
      throw new UnsupportedOperationException("Task info is not being kept!");
    }
    return (TaskInfo[]) this.taskList.toArray(new TaskInfo[this.taskList.size()]);
  }


  /**
   * Return a short description of the total running time.
   */
  public String shortSummary() {
    return "StopWatch '" + this.id + "': running time (millis) = " + getTotalTimeMillis();
  }

  /**
   * Return a string with a table describing all tasks performed.
   * For custom reporting, call getTaskInfo() and use the task info directly.
   */
  public String prettyPrint() {
    StringBuffer sb = new StringBuffer(shortSummary());
    sb.append('\n');
    if (!this.keepTaskList) {
      sb.append("No task info kept");
    }
    else {
      TaskInfo[] tasks = getTaskInfo();
      sb.append("-----------------------------------------\n");
      sb.append("ms     %     Task name\n");
      sb.append("-----------------------------------------\n");
      NumberFormat nf = NumberFormat.getNumberInstance();
      nf.setMinimumIntegerDigits(5);
      nf.setGroupingUsed(false);
      NumberFormat pf = NumberFormat.getPercentInstance();
      pf.setMinimumIntegerDigits(3);
      pf.setGroupingUsed(false);
      for (int i = 0; i < tasks.length; i++) {
        sb.append(nf.format(tasks[i].getTimeMillis()) + "  ");
        sb.append(pf.format(tasks[i].getTimeSeconds() / getTotalTimeSeconds()) + "  ");
        sb.append(tasks[i].getTaskName() + "\n");
      }
    }
    return sb.toString();
  }

  /**
   * Return an informative string describing all tasks performed
   * For custom reporting, call <code>getTaskInfo()</code> and use the task info directly.
   */
  public String toString() {
    StringBuffer sb = new StringBuffer(shortSummary());
    if (this.keepTaskList) {
      TaskInfo[] tasks = getTaskInfo();
      for (int i = 0; i < tasks.length; i++) {
        sb.append("; [" + tasks[i].getTaskName() + "] took " + tasks[i].getTimeMillis());
        long percent = Math.round((100.0 * tasks[i].getTimeSeconds()) / getTotalTimeSeconds());
        sb.append(" = " + percent + "%");
      }
    }
    else {
      sb.append("; no task info kept");
    }
    return sb.toString();
  }


  /**
   * Inner class to hold data about one task executed within the stop watch.
   */
  public static class TaskInfo {

    private final String taskName;

    private final long timeMillis;

    private TaskInfo(String taskName, long timeMillis) {
      this.taskName = taskName;
      this.timeMillis = timeMillis;
    }

    /**
     * Return the name of this task.
     */
    public String getTaskName() {
      return taskName;
    }

    /**
     * Return the time in milliseconds this task took.
     */
    public long getTimeMillis() {
      return timeMillis;
    }

    /**
     * Return the time in seconds this task took.
     */
    public double getTimeSeconds() {
      return timeMillis / 1000.0;
    }
  }

}

   
    
  








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