|
Java INDEPENDENT TOPIC 05 – TIMING
LESSON NOTE
APPROACH 1 – System.nanoTime() One
can use System.nanoTime()
to get an initial nanosecond reading.
Note that alone, this value is not valuable. But if we take a second reading, we can
then take the difference between the two values and that will be the time in nano seconds that has passed between the readings. Note
that nanoseconds are very small amounts of time. So we tend to have very big numbers when we
deal with a measurement of time in nanoseconds. Therefore, instead of using int variables,
we use long variables. EXAMPLE CODE The
following example takes two readings and stores thoses
values in t1 and t2. The difference of
the two readings in the elapsed time between readings in nano
seconds. long t1 = System.nanoTime(); //Add some statements here long t2 = System.nanoTime(); long dif = t2 – t1; System.out.println("The time that has
passed is " + dif + " nanoseconds. "); APPROACH 2
– System.currentTimeMillis() One
can also use System.currentTimeMillis() to get the
number of milliseconds that have passed since January 1st
1970. While a single reading is
usable, we still tend to use this at take the difference between two readings
to get the elapsed time in milliseconds. EXAMPLE CODE Below
you will find the exact same approach as above but for milliseconds. long t1 = System.currentTimeMillis(); //Add some statements here long t2 = System.currentTimeMillis(); long dif = t2 – t1; System.out.println("The time that has
passed is " + dif + " milliseconds. "); CONVERTING
TO SECONDS We
can convert nanoseconds to seconds by dividing by 1,000,000,000 (one billion).
|
|
|
