How to convert nanoseconds to seconds using the TimeUnit enum?
JavaTimeunitJava Problem Overview
How to convert a value from nanoseconds to seconds?
Here's the code segment:
import java.io.*;
import java.util.concurrent.*;
..
class Stamper {
public static void main (String[] args) {
long start = System.nanoTime();
//some try with nested loops
long end = System.nanoTime();
long elapsedTime = end - start;
System.out.println("elapsed: " + elapsedTime + "nano seconds\n");
//convert to seconds
TimeUnit seconds = new TimeUnit();
System.out.println("which is " + seconds.toSeconds(elapsedTime) + " seconds");
}}
The error is
Stamper.java:16: enum types may not be instantiated.
What does this mean?
Java Solutions
Solution 1 - Java
TimeUnit Enum
The following expression uses the TimeUnit enum (Java 5 and later) to convert from nanoseconds to seconds:
TimeUnit.SECONDS.convert(elapsedTime, TimeUnit.NANOSECONDS)
Solution 2 - Java
Well, you could just divide by 1,000,000,000:
long elapsedTime = end - start;
double seconds = (double)elapsedTime / 1_000_000_000.0;
If you use TimeUnit to convert, you'll get your result as a long, so you'll lose decimal precision but maintain whole number precision.
Solution 3 - Java
TimeUnit is an enum, so you can't create a new one.
The following will convert 1000000000000ns to seconds.
TimeUnit.NANOSECONDS.toSeconds(1000000000000L);
Solution 4 - Java
To reduce verbosity, you can use a static import:
import static java.util.concurrent.TimeUnit.NANOSECONDS;
-and henceforth just type
NANOSECONDS.toSeconds(elapsedTime);
Solution 5 - Java
You should write :
long startTime = System.nanoTime();
long estimatedTime = System.nanoTime() - startTime;
Assigning the endTime in a variable might cause a few nanoseconds. In this approach you will get the exact elapsed time.
And then:
TimeUnit.SECONDS.convert(estimatedTime, TimeUnit.NANOSECONDS)
Solution 6 - Java
This will convert a time to seconds in a double format, which is more precise than an integer value:
double elapsedTimeInSeconds = TimeUnit.MILLISECONDS.convert(elapsedTime, TimeUnit.NANOSECONDS) / 1000.0;
Solution 7 - Java
JDK9+ solution using java.time.Duration
Duration.ofNanos(1_000_000L).toSeconds()
https://docs.oracle.com/javase/9/docs/api/java/time/Duration.html#ofNanos-long-
https://docs.oracle.com/javase/9/docs/api/java/time/Duration.html#toSeconds--
Solution 8 - Java
In Java 8 or Kotlin, I use Duration.ofNanos(1_000_000_000) like
val duration = Duration.ofNanos(1_000_000_000)
logger.info(String.format("%d %02dm %02ds %03d",
elapse, duration.toMinutes(), duration.toSeconds(), duration.toMillis()))
Read more https://docs.oracle.com/javase/8/docs/api/java/time/Duration.html