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/* |
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* Written by members of JCP JSR-166 Expert Group and released to the |
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* public domain. Use, modify, and redistribute this code in any way |
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* without acknowledgement. Other contributors include Andrew Wright, |
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* Jeffrey Hayes, Pat Fischer, Mike Judd. |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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* Other contributors include Andrew Wright, Jeffrey Hayes, |
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* Pat Fisher, Mike Judd. |
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*/ |
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import junit.framework.*; |
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import junit.framework.Test; |
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import junit.framework.TestSuite; |
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public class SystemTest extends TestCase { |
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public class SystemTest extends JSR166TestCase { |
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public static void main(String[] args) { |
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junit.textui.TestRunner.run(suite()); |
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main(suite(), args); |
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} |
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public static Test suite() { |
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return new TestSuite(SystemTest.class); |
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return new TestSuite(SystemTest.class); |
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} |
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public void testNanoTime1() { |
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// Nanos between readings of millis must be no longer than millis |
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/** |
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* Worst case rounding for millisecs; set for 60 cycle millis clock. |
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* This value might need to be changed on JVMs with coarser |
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* System.currentTimeMillis clocks. |
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*/ |
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static final long MILLIS_ROUND = 17; |
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|
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/** |
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* Nanos between readings of millis is no longer than millis (plus |
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* possible rounding), and vice versa. |
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* This shows only that nano timing not (much) worse than milli. |
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*/ |
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public void testNanoTime() throws InterruptedException { |
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long m0 = System.currentTimeMillis(); |
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long n0 = System.nanoTime(); |
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Thread.sleep(1); |
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long m1 = System.currentTimeMillis(); |
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long n1 = System.nanoTime(); |
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// Ensure some computation that is not optimized away. |
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long sum = 0; |
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for (long i = 1; i < 10000; ++i) |
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sum += i; |
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assertTrue(sum != 0); |
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|
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long n2 = System.nanoTime(); |
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for (long i = 1; i < 10000; ++i) |
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sum -= i; |
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assertTrue(sum == 0); |
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|
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long m2 = System.currentTimeMillis(); |
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long millis = m2 - m1; |
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long nanos = n2 - n1; |
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assertTrue(nanos >= 0); |
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assertTrue(nanos <= millis * 1000000); |
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} |
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public void testNanoTime2() { |
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// Millis between readings of nanos must be no longer than nanos |
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long n1 = System.nanoTime(); |
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long m1 = System.currentTimeMillis(); |
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// Ensure some computation that is not optimized away. |
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long sum = 0; |
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for (long i = 1; i < 10000; ++i) |
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sum += i; |
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assertTrue(sum != 0); |
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Thread.sleep(50); // avoid possibly scaled SHORT_DELAY_MS |
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long m2 = System.currentTimeMillis(); |
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for (long i = 1; i < 10000; ++i) |
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sum -= i; |
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assertTrue(sum == 0); |
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long n2 = System.nanoTime(); |
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long millis = m2 - m1; |
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long nanos = n2 - n1; |
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assertTrue(nanos >= 0); |
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assertTrue(millis * 1000000 <= nanos); |
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Thread.sleep(1); |
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long m3 = System.currentTimeMillis(); |
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long n3 = System.nanoTime(); |
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assertTrue((n2 - n1) / 1_000_000 <= m3 - m0 + MILLIS_ROUND); |
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assertTrue(m2 - m1 <= (n3 - n0) / 1_000_000 + MILLIS_ROUND); |
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} |
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} |
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