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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