StopWatch.java Source code

Introduction

Here is the source code for StopWatch.java

Source

import java.io.PrintWriter;

/**
 * Prints time durations; used for development purposes only.
 * 
 * No threads or system resources are harmed in the making of a stop watch. A
 * stop watch simply remembers the start time (and elapsed time when paused) and
 * prints the total "running" time when either {@link #mark} or
 * {@link #stop} is called.
 * 
 * {@link #stop} doesn't really stop anything. You can call stop as many times
 * as you like and it will print the time elapsed since start. It would be easy
 * to change this behavior, but I haven't needed to.
 * 
 * @author Jim Menard, <a href="mailto:jimm@io.com">jimm@io.com</a>
 */
public class StopWatch {

    protected String name;

    protected long t0;

    protected long elapsedTime;

    protected PrintWriter out;

    public StopWatch() {
        this(null, null);
    }

    public StopWatch(String name) {
        this(name, null);
    }

    public StopWatch(PrintWriter out) {
        this(null, out);
    }

    public StopWatch(String name, PrintWriter out) {
        this.name = name;
        if (out == null)
            this.out = new PrintWriter(System.err);
        else
            this.out = out;
        elapsedTime = -1L; // So we can tell if we are ever started
    }

    /**
     * Remembers the current time and prints a message.
     */
    public void start() {
        start(true);
    }

    /**
     * Remembers the current time and prints a message if requested.
     * 
     * @param printStarting
     *          if <code>true</code> and this stop watch has a name, print a
     *          message
     */
    public void start(boolean printStarting) {
        if (t0 != 0)
            System.err.println("(warning: StopWatch already started; resetting)");
        if (printStarting && name != null)
            System.err.println("starting " + name);
        elapsedTime = 0;
        t0 = System.currentTimeMillis();
    }

    /**
     * Pauses the stop watch.
     */
    public void pause() {
        long now = System.currentTimeMillis();
        elapsedTime += now - t0;
        t0 = 0;
    }

    /**
     * Resumes the stop watch.
     */
    public void resume() {
        t0 = System.currentTimeMillis();
    }

    /**
     * Prints the current elapsed time without stopping.
     */
    public void mark() {
        stop(null, true);
    }

    /**
     * Prints the current elapsed time without stopping, along with the stop watch
     * name if <var>printMark</var> is <code>true</code>.
     * 
     * @param printMark
     *          if <code>true</code>, the stop watch name will be printed
     */
    public void mark(boolean printMark) {
        stop(null, printMark);
    }

    /**
     * Prints the current elapsed time without stopping, along with the stop watch
     * name and <var>msg</var>.
     * 
     * @param msg
     *          a message to print
     */
    public void mark(String msg) {
        stop(msg, true);
    }

    /**
     * Prints the current elapsed time without stopping, along with, along with
     * the stop watch name if <var>printMark</var> is <code>true</code> and the
     * <var>msg</var> if it's not <code>null</code>.
     * 
     * @param msg
     *          a message to print
     * @param printMark
     *          if <code>true</code>, the stop watch name will be printed
     */
    public void mark(String msg, boolean printMark) {
        stop(msg, printMark);
    }

    /**
     * Stops the stop watch and prints the name of this stop watch and the current
     * elapsed time.
     */
    public void stop() {
        stop(null, true);
    }

    /**
     * Stops the stop watch and prints the name of this stop watch, <var>msg</var>
     * if non-<code>null</code>, and the current elapsed time.
     * 
     * @param msg
     *          a message to print; may be <code>null</code>
     */
    public void stop(String msg) {
        stop(msg, true);
    }

    /**
     * Prints the current elapsed time, along with the stop watch name if
     * <var>printMark</var> is <code>true</code> and the <var>msg</var> if
     * it's not <code>null</code>.
     * 
     * @param msg
     *          a message to print; may be <code>null</code>
     * @param printName
     *          if <code>true</code>, the stop watch name will be printed
     */
    public void stop(String msg, boolean printName) {
        long now = System.currentTimeMillis();

        if (elapsedTime == -1) {
            System.err.println("(StopWatch" + (name != null ? (" \"" + name + '"') : "")
                    + " was stopped without ever being started)");
            return;
        }

        long total = elapsedTime;
        if (t0 != 0)
            total += now - t0;

        String separator = null;
        if (printName && name != null) {
            System.err.print(name);
            separator = ": ";
        }
        if (msg != null) {
            if (separator != null)
                System.err.print(' ');
            System.err.print("(" + msg + ")");
            separator = ": ";
        }
        if (separator != null)
            System.err.print(separator);

        System.err.println("" + (total / 1000.0) + " seconds");
    }

}