Using Spring and Apache Commons StopWatch to Monitor Java Code Execution Time

Background

When developing Java applications, measuring the execution time of tasks or code blocks is often done by printing the difference between start and end timestamps, which can become cumbersome and error‑prone, especially for complex or undocumented code sections.

This article introduces utility classes—Spring's org.springframework.util.StopWatch , Apache Commons Lang3 org.apache.commons.lang.time.StopWatch , and Guava's stopwatch—as convenient solutions for such scenarios.

Spring StopWatch Usage

The Spring StopWatch, located in the org.springframework.util package, provides millisecond‑level timing for synchronous single‑threaded code. To use it, include the Spring core dependency (already present in Spring MVC/Boot) and instantiate the class.

public static void main(String[] args) throws InterruptedException {
    StopWatch stopWatch = new StopWatch();
    // Task 1
    stopWatch.start("TaskOneName");
    Thread.sleep(1000 * 3);
    System.out.println("Current task: " + stopWatch.currentTaskName());
    stopWatch.stop();
    // Task 2
    stopWatch.start("TaskTwoName");
    Thread.sleep(1000 * 10);
    System.out.println("Current task: " + stopWatch.currentTaskName());
    stopWatch.stop();
    // Task 3
    stopWatch.start("TaskThreeName");
    Thread.sleep(1000 * 10);
    System.out.println("Current task: " + stopWatch.currentTaskName());
    stopWatch.stop();
    System.out.println(stopWatch.prettyPrint());
    System.out.println(stopWatch.shortSummary());
    System.out.println(stopWatch.currentTaskName()); // null after stop
    System.out.println(stopWatch.getLastTaskName());
    System.out.println(stopWatch.getLastTaskInfo());
    System.out.println("Total time: " + sw.getTotalTimeMillis());
    System.out.println("Task count: " + sw.getTaskCount());
    System.out.println("All task details: " + sw.getTaskInfo());
}

The StopWatch records each task's duration, provides detailed summaries, and can output total time, task count, and individual task information.

Spring StopWatch Source Highlights

public class StopWatch {
    private final String id;
    private boolean keepTaskList = true;
    private final List
taskList;
    private long startTimeMillis;
    private boolean running;
    private String currentTaskName;
    private StopWatch.TaskInfo lastTaskInfo;
    private int taskCount;
    private long totalTimeMillis;
    ...
}

Key fields include the unique ID, task list, start time, running flag, current task name, last task info, task count, and total elapsed time.

Important Notes for Spring StopWatch

Not thread‑safe; avoid synchronization.

Only one task can be active per instance.

A new task cannot be started before the previous one is stopped.

To time multiple concurrent tasks, create separate StopWatch instances.

Apache Commons StopWatch Usage

Apache's StopWatch (from org.apache.commons.lang3 ) offers similar functionality with additional features such as split, suspend, and resume.

public static void main(String[] args) throws InterruptedException {
    StopWatch watch = StopWatch.createStarted();
    Thread.sleep(1000);
    System.out.println(watch.getTime());
    System.out.println("Elapsed since start: " + watch.getTime() + "ms");
    Thread.sleep(1000);
    watch.split();
    System.out.println("Time to first split: " + watch.getSplitTime());
    Thread.sleep(1000);
    watch.split();
    System.out.println("Time to second split: " + watch.getSplitTime());
    watch.reset();
    watch.start();
    Thread.sleep(1000);
    System.out.println("After reset: " + watch.getTime());
    watch.suspend();
    System.out.println("Suspended for 2 seconds");
    Thread.sleep(2000);
    watch.resume();
    System.out.println("After resume: " + watch.getTime());
    Thread.sleep(1000);
    watch.stop();
    System.out.println("Final time: " + watch.getTime() + "ms");
    System.out.println("Final time (seconds): " + watch.getTime(TimeUnit.SECONDS) + "s");
}

The Apache StopWatch supports start‑stop, split points, reset, suspend, and resume, making it flexible for detailed performance analysis.

Conclusion

Using dedicated stopwatch utilities like Spring's and Apache Commons' StopWatch simplifies performance profiling, produces cleaner logs, and offers richer timing data compared to manual timestamp calculations, helping developers write more efficient and maintainable Java code.