How to work out how long it takes to sum numbers in jav

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Java

In this method, it must use the static nanoTime method of the java.lang.System class to time how long it takes to sum the first n integer values. It must print the number of nanoseconds after the loop.
At the moment the method i have, the numbers have already been added up before i start the time, so how could i change it so it is correct.

What I have tried:

<pre>public static void timing(int n)
    {
        long sum = 0;
        for(int i = 1; i <= n; i++) {
            sum += i;
        }
        // Print out the time it took in nanoseconds.
        long startTime = System.nanoTime();
        long elapsedNanos = System.nanoTime() - startTime;
        System.out.println(elapsedNanos);
    }