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dl |
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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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*/ |
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import junit.framework.*; |
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public class SystemTest extends TestCase { |
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public static void main(String[] args) { |
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junit.textui.TestRunner.run(suite()); |
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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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} |
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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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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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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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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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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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} |
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} |
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