com.pushinginertia.commons.lang.logging.Timer.java Source code

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Here is the source code for com.pushinginertia.commons.lang.logging.Timer.java

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/* Copyright (c) 2011-2014 Pushing Inertia
 * All rights reserved.  http://pushinginertia.com
 *
 * 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 com.pushinginertia.commons.lang.logging;

import org.joda.time.Duration;

import java.util.concurrent.TimeUnit;

/**
 * Provides a very simple timer for logging the time it takes to complete units of work.
 */
public class Timer {
    private long startNs;

    /**
     * Provides a very simple timer for logging the time it takes to complete units of work.
     */
    public Timer() {
        this.startNs = nanoTime();
    }

    /**
     * Package rotected method available to initialize the start time in a unit test.
     * @param startNs
     */
    Timer(final long startNs) {
        this.startNs = startNs;
    }

    /**
     * Resets the timer to a duration of zero.
     */
    public void reset() {
        this.startNs = nanoTime();
    }

    /**
     * The elapsed time in milliseconds since this object was instantiated.
     * @return elapsed time in milliseconds
     */
    public long elapsedMs() {
        final long elapsedNs = nanoTime() - startNs;
        return TimeUnit.NANOSECONDS.toMillis(elapsedNs);
    }

    /**
     * Creates a {@link Duration} instance containing the elapsed milliseconds since this object was instantiated.
     * @return new immutable instance
     */
    public Duration toDuration() {
        return Duration.millis(elapsedMs());
    }

    /**
     * Returns the current nanotime by calling {@link System#nanoTime()}. Wrapped in a method for easy overriding in a
     * unit test.
     * @return value of {@link System#nanoTime()}
     */
    protected long nanoTime() {
        return System.nanoTime();
    }
}