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/*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/publicdomain/zero/1.0/
* Other contributors include Andrew Wright, Jeffrey Hayes,
* Pat Fisher, Mike Judd.
*/
package jsr166;
import junit.framework.*;
public class SystemTest extends JSR166TestCase {
/**
* Worst case rounding for millisecs; set for 60 cycle millis clock.
* This value might need to be changed on JVMs with coarser
* System.currentTimeMillis clocks.
*/
static final long MILLIS_ROUND = 17;
/**
* Nanos between readings of millis is no longer than millis (plus
* possible rounding).
* This shows only that nano timing not (much) worse than milli.
*/
public void testNanoTime1() throws InterruptedException {
long m1 = System.currentTimeMillis();
Thread.sleep(1);
long n1 = System.nanoTime();
Thread.sleep(SHORT_DELAY_MS);
long n2 = System.nanoTime();
Thread.sleep(1);
long m2 = System.currentTimeMillis();
long millis = m2 - m1;
long nanos = n2 - n1;
assertTrue(nanos >= 0);
long nanosAsMillis = nanos / 1000000;
assertTrue(nanosAsMillis <= millis + MILLIS_ROUND);
}
/**
* Millis between readings of nanos is less than nanos, adjusting
* for rounding.
* This shows only that nano timing not (much) worse than milli.
*/
public void testNanoTime2() throws InterruptedException {
long n1 = System.nanoTime();
Thread.sleep(1);
long m1 = System.currentTimeMillis();
Thread.sleep(SHORT_DELAY_MS);
long m2 = System.currentTimeMillis();
Thread.sleep(1);
long n2 = System.nanoTime();
long millis = m2 - m1;
long nanos = n2 - n1;
assertTrue(nanos >= 0);
long nanosAsMillis = nanos / 1000000;
assertTrue(millis <= nanosAsMillis + MILLIS_ROUND);
}
}
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