1 /*
 2  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 3  *
 4  * This code is free software; you can redistribute it and/or modify it
 5  * under the terms of the GNU General Public License version 2 only, as
 6  * published by the Free Software Foundation.
 7  *
 8  * This code is distributed in the hope that it will be useful, but WITHOUT
 9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
11  * version 2 for more details (a copy is included in the LICENSE file that
12  * accompanied this code).
13  *
14  * You should have received a copy of the GNU General Public License version
15  * 2 along with this work; if not, write to the Free Software Foundation,
16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17  *
18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19  * or visit www.oracle.com if you need additional information or have any
20  * questions.
21  */
22 
23 /*
24  * This file is available under and governed by the GNU General Public
25  * License version 2 only, as published by the Free Software Foundation.
26  * However, the following notice accompanied the original version of this
27  * file:
28  *
29  * Written by Doug Lea with assistance from members of JCP JSR-166
30  * Expert Group and released to the public domain, as explained at
31  * http://creativecommons.org/publicdomain/zero/1.0/
32  * Other contributors include Andrew Wright, Jeffrey Hayes,
33  * Pat Fisher, Mike Judd.
34  */
35 
36 import junit.framework.Test;
37 import junit.framework.TestSuite;
38 
39 public class SystemTest extends JSR166TestCase {
40     public static void main(String[] args) {
41         main(suite(), args);
42     }
43 
44     public static Test suite() {
45         return new TestSuite(SystemTest.class);
46     }
47 
48     /**
49      * Worst case rounding for millisecs; set for 60 cycle millis clock.
50      * This value might need to be changed on JVMs with coarser
51      * System.currentTimeMillis clocks.
52      */
53     static final long MILLIS_ROUND = 17;
54 
55     /**
56      * Nanos between readings of millis is no longer than millis (plus
57      * possible rounding), and vice versa.
58      * This shows only that nano timing not (much) worse than milli.
59      */
60     public void testNanoTime() throws InterruptedException {
61         long m0 = System.currentTimeMillis();
62         long n0 = System.nanoTime();
63         Thread.sleep(1);
64         long m1 = System.currentTimeMillis();
65         long n1 = System.nanoTime();
66         Thread.sleep(50);       // avoid possibly scaled SHORT_DELAY_MS
67         long m2 = System.currentTimeMillis();
68         long n2 = System.nanoTime();
69         Thread.sleep(1);
70         long m3 = System.currentTimeMillis();
71         long n3 = System.nanoTime();
72         assertTrue((n2 - n1) / 1_000_000 <= m3 - m0 + MILLIS_ROUND);
73         assertTrue(m2 - m1 <= (n3 - n0) / 1_000_000 + MILLIS_ROUND);
74     }
75 }