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      1 /*
      2  * Written by Doug Lea with assistance from members of JCP JSR-166
      3  * Expert Group and released to the public domain, as explained at
      4  * http://creativecommons.org/publicdomain/zero/1.0/
      5  */
      6 
      7 package jsr166;
      8 
      9 import java.util.concurrent.Executors;
     10 import java.util.concurrent.ExecutorService;
     11 import java.util.concurrent.Phaser;
     12 import java.util.concurrent.atomic.LongAccumulator;
     13 
     14 import junit.framework.Test;
     15 import junit.framework.TestSuite;
     16 
     17 public class LongAccumulatorTest extends JSR166TestCase {
     18     // android-note: Removed because the CTS runner does a bad job of
     19     // retrying tests that have suite() declarations.
     20     //
     21     // public static void main(String[] args) {
     22     //     main(suite(), args);
     23     // }
     24     // public static Test suite() {
     25     //     return new TestSuite(LongAccumulatorTest.class);
     26     // }
     27 
     28     /**
     29      * default constructed initializes to zero
     30      */
     31     public void testConstructor() {
     32         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
     33         assertEquals(0, ai.get());
     34     }
     35 
     36     /**
     37      * accumulate accumulates given value to current, and get returns current value
     38      */
     39     public void testAccumulateAndGet() {
     40         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
     41         ai.accumulate(2);
     42         assertEquals(2, ai.get());
     43         ai.accumulate(-4);
     44         assertEquals(2, ai.get());
     45         ai.accumulate(4);
     46         assertEquals(4, ai.get());
     47     }
     48 
     49     /**
     50      * reset() causes subsequent get() to return zero
     51      */
     52     public void testReset() {
     53         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
     54         ai.accumulate(2);
     55         assertEquals(2, ai.get());
     56         ai.reset();
     57         assertEquals(0, ai.get());
     58     }
     59 
     60     /**
     61      * getThenReset() returns current value; subsequent get() returns zero
     62      */
     63     public void testGetThenReset() {
     64         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
     65         ai.accumulate(2);
     66         assertEquals(2, ai.get());
     67         assertEquals(2, ai.getThenReset());
     68         assertEquals(0, ai.get());
     69     }
     70 
     71     /**
     72      * toString returns current value.
     73      */
     74     public void testToString() {
     75         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
     76         assertEquals("0", ai.toString());
     77         ai.accumulate(1);
     78         assertEquals(Long.toString(1), ai.toString());
     79     }
     80 
     81     /**
     82      * intValue returns current value.
     83      */
     84     public void testIntValue() {
     85         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
     86         assertEquals(0, ai.intValue());
     87         ai.accumulate(1);
     88         assertEquals(1, ai.intValue());
     89     }
     90 
     91     /**
     92      * longValue returns current value.
     93      */
     94     public void testLongValue() {
     95         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
     96         assertEquals(0, ai.longValue());
     97         ai.accumulate(1);
     98         assertEquals(1, ai.longValue());
     99     }
    100 
    101     /**
    102      * floatValue returns current value.
    103      */
    104     public void testFloatValue() {
    105         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    106         assertEquals(0.0f, ai.floatValue());
    107         ai.accumulate(1);
    108         assertEquals(1.0f, ai.floatValue());
    109     }
    110 
    111     /**
    112      * doubleValue returns current value.
    113      */
    114     public void testDoubleValue() {
    115         LongAccumulator ai = new LongAccumulator(Long::max, 0L);
    116         assertEquals(0.0, ai.doubleValue());
    117         ai.accumulate(1);
    118         assertEquals(1.0, ai.doubleValue());
    119     }
    120 
    121     /**
    122      * accumulates by multiple threads produce correct result
    123      */
    124     public void testAccumulateAndGetMT() {
    125         final int incs = 1000000;
    126         final int nthreads = 4;
    127         final ExecutorService pool = Executors.newCachedThreadPool();
    128         LongAccumulator a = new LongAccumulator(Long::max, 0L);
    129         Phaser phaser = new Phaser(nthreads + 1);
    130         for (int i = 0; i < nthreads; ++i)
    131             pool.execute(new AccTask(a, phaser, incs));
    132         phaser.arriveAndAwaitAdvance();
    133         phaser.arriveAndAwaitAdvance();
    134         long expected = incs - 1;
    135         long result = a.get();
    136         assertEquals(expected, result);
    137         pool.shutdown();
    138     }
    139 
    140     static final class AccTask implements Runnable {
    141         final LongAccumulator acc;
    142         final Phaser phaser;
    143         final int incs;
    144         volatile long result;
    145         AccTask(LongAccumulator acc, Phaser phaser, int incs) {
    146             this.acc = acc;
    147             this.phaser = phaser;
    148             this.incs = incs;
    149         }
    150 
    151         public void run() {
    152             phaser.arriveAndAwaitAdvance();
    153             LongAccumulator a = acc;
    154             for (int i = 0; i < incs; ++i)
    155                 a.accumulate(i);
    156             result = a.get();
    157             phaser.arrive();
    158         }
    159     }
    160 
    161 }
    162