Mastering Code Timing in Java: Spring and Apache StopWatch Deep Dive

Background

Measuring the execution time of code by manually printing start and end timestamps becomes cumbersome when many tasks need timing. Utility classes provide a cleaner approach.

Spring org.springframework.util.StopWatch

Dependency

<!-- https://mvnrepository.com/artifact/org.springframework/spring-core -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>${spring.version}</version>
</dependency>

Usage example

public static void main(String[] args) throws InterruptedException {
    StopWatch sw = new StopWatch();
    sw.start("TaskOne");
    Thread.sleep(3000);
    System.out.println("Current task: " + sw.currentTaskName());
    sw.stop();

    sw.start("TaskTwo");
    Thread.sleep(10000);
    System.out.println("Current task: " + sw.currentTaskName());
    sw.stop();

    sw.start("TaskThree");
    Thread.sleep(10000);
    System.out.println("Current task: " + sw.currentTaskName());
    sw.stop();

    System.out.println(sw.prettyPrint());
    System.out.println(sw.shortSummary());
    System.out.println("Total time: " + sw.getTotalTimeMillis() + " ms");
}

Key methods:

new StopWatch() – creates a stopwatch without starting a task.

start(String taskName) – begins timing a named task.

stop() – stops the current task.

currentTaskName() – returns the name of the running task.

prettyPrint() – detailed timing for all tasks.

shortSummary() – concise summary of total time.

getTotalTimeMillis() – total elapsed time in milliseconds.

Notes:

The class is not thread‑safe; use separate instances for concurrent timing.

Only one task can be active at a time; a new task must be started after the previous one is stopped.

Apache Commons Lang org.apache.commons.lang3.time.StopWatch

Dependency

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.6</version>
</dependency>

Usage example

public static void main(String[] args) throws InterruptedException {
    StopWatch watch = StopWatch.createStarted();
    Thread.sleep(1000);
    System.out.println("Elapsed: " + watch.getTime() + " ms");

    watch.split();
    System.out.println("Split time: " + watch.getSplitTime() + " ms");

    watch.reset();
    watch.start();
    Thread.sleep(1000);
    System.out.println("After reset: " + watch.getTime() + " ms");

    watch.suspend();
    Thread.sleep(2000);
    watch.resume();
    Thread.sleep(1000);
    watch.stop();
    System.out.println("Final elapsed: " + watch.getTime() + " ms");
    System.out.println("Elapsed in seconds: " + watch.getTime(TimeUnit.SECONDS) + " s");
}

Important methods:

createStarted() – creates and starts a stopwatch.

start() – starts timing (if not already started).

stop() – stops the current task.

split() – records a split point.

unsplit() – clears the split point.

reset() – clears all timing data.

suspend() / resume() – pause and continue timing.

getTime() – elapsed time since start or last reset.

getSplitTime() – time from start to the most recent split.

getTime(TimeUnit) – elapsed time in the specified unit.

Notes:

Not designed for concurrent use; each instance can time only one task at a time.

Supports split, suspend, and reset operations that Spring’s StopWatch does not provide.

Conclusion

Both org.springframework.util.StopWatch and org.apache.commons.lang3.time.StopWatch simplify performance measurement compared with manual timestamp calculations. Spring’s implementation is lightweight and suited for sequential single‑threaded tasks, while Apache Commons Lang adds split, suspend, and reset capabilities for more flexible timing scenarios.