What's the Most Accurate Way to Measure Elapsed Time in Java?

Measuring Time Elapsed in Java

To measure time elapsed in Java, several methods are available. However, the most accurate and efficient approach is to utilize the System.nanoTime() method.

Contrary to popular belief, System.currentTimeMillis() is not suitable for measuring elapsed time, as it relies on wall-clock time, which is prone to drift and manual corrections.

System.nanoTime(), on the other hand, is designed specifically for measuring elapsed time and is unaffected by wall-clock adjustments. It operates at a much finer granularity, typically microseconds or nanoseconds.

To illustrate its usage, let's consider the following class:

public class Stream {
    private long startTime;
    private long endTime;

    public void setStartTime() {
        startTime = System.nanoTime();
    }

    public void setEndTime() {
        endTime = System.nanoTime();
    }

    public long getDuration() {
        return endTime - startTime;
    }
}

By invoking the setStartTime() and setEndTime() methods within relevant code blocks, you can capture the timestamps. Subsequently, calling getDuration() will accurately calculate the time elapsed from the start to the end in nanoseconds, which can be easily converted to the appropriate unit (e.g., milliseconds, seconds, or minutes).

Remember, while System.nanoTime() offers high precision timing, its results can also be affected by factors such as the operating system, hardware, and other processes running concurrently.

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