concurrent/src/test/java/AtomicIntegerArrayTest.java

/*
 * 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/licenses/publicdomain
 * Other contributors include Andrew Wright, Jeffrey Hayes, 
 * Pat Fisher, Mike Judd. 
 */

import junit.framework.*;
import java.util.concurrent.atomic.*;
import java.io.*;
import java.util.*;

public class AtomicIntegerArrayTest extends JSR166TestCase {

    public static void main (String[] args) {
        junit.textui.TestRunner.run (suite());
    }
    public static Test suite() {
        return new TestSuite(AtomicIntegerArrayTest.class);
    }


    /**
     * constructor creates array of given size with all elements zero
     */
    public void testConstructor() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE);
        for (int i = 0; i < SIZE; ++i) 
            assertEquals(0,ai.get(i));
    }

    /**
     * constructor with null array throws NPE
     */
    public void testConstructor2NPE() {
        try {
            int[] a = null;
            AtomicIntegerArray ai = new AtomicIntegerArray(a);
        } catch (NullPointerException success) {
        } catch (Exception ex) {
            unexpectedException();
        }
    }

    /**
     * constructor with array is of same size and has all elements
     */
    public void testConstructor2() {
        int[] a = { 17, 3, -42, 99, -7};
        AtomicIntegerArray ai = new AtomicIntegerArray(a);
        assertEquals(a.length, ai.length());
        for (int i = 0; i < a.length; ++i) 
            assertEquals(a[i], ai.get(i));
    }

    /**
     * get and set for out of bound indices throw IndexOutOfBoundsException
     */
    public void testIndexing(){
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE);
        try {
            ai.get(SIZE);
        } catch(IndexOutOfBoundsException success){
        }
        try {
            ai.get(-1);
        } catch(IndexOutOfBoundsException success){
        }
        try {
            ai.set(SIZE, 0);
        } catch(IndexOutOfBoundsException success){
        }
        try {
            ai.set(-1, 0);
        } catch(IndexOutOfBoundsException success){
        }
    }

    /**
     * get returns the last value set at index
     */
    public void testGetSet() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertEquals(1,ai.get(i));
            ai.set(i, 2);
            assertEquals(2,ai.get(i));
            ai.set(i, -3);
            assertEquals(-3,ai.get(i));
        }
    }

    /**
     * compareAndSet succeeds in changing value if equal to expected else fails
     */
    public void testCompareAndSet() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertTrue(ai.compareAndSet(i, 1,2));
            assertTrue(ai.compareAndSet(i, 2,-4));
            assertEquals(-4,ai.get(i));
            assertFalse(ai.compareAndSet(i, -5,7));
            assertFalse((7 == ai.get(i)));
            assertTrue(ai.compareAndSet(i, -4,7));
            assertEquals(7,ai.get(i));
        }
    }

    /**
     * compareAndSet in one thread enables another waiting for value
     * to succeed
     */
    public void testCompareAndSetInMultipleThreads() {
        final AtomicIntegerArray a = new AtomicIntegerArray(1);
        a.set(0, 1);
        Thread t = new Thread(new Runnable() {
                public void run() {
                    while(!a.compareAndSet(0, 2, 3)) Thread.yield();
                }});
        try {
            t.start();
            assertTrue(a.compareAndSet(0, 1, 2));
            t.join(LONG_DELAY_MS);
            assertFalse(t.isAlive());
            assertEquals(a.get(0), 3);
        }
        catch(Exception e) {
            unexpectedException();
        }
    }

    /**
     * repeated weakCompareAndSet succeeds in changing value when equal
     * to expected 
     */
    public void testWeakCompareAndSet() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            while(!ai.weakCompareAndSet(i, 1,2));
            while(!ai.weakCompareAndSet(i, 2,-4));
            assertEquals(-4,ai.get(i));
            while(!ai.weakCompareAndSet(i, -4,7));
            assertEquals(7,ai.get(i));
        }
    }

    /**
     *  getAndSet returns previous value and sets to given value at given index
     */
    public void testGetAndSet() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertEquals(1,ai.getAndSet(i,0));
            assertEquals(0,ai.getAndSet(i,-10));
            assertEquals(-10,ai.getAndSet(i,1));
        }
    }

    /**
     *  getAndAdd returns previous value and adds given value
     */
    public void testGetAndAdd() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertEquals(1,ai.getAndAdd(i,2));
            assertEquals(3,ai.get(i));
            assertEquals(3,ai.getAndAdd(i,-4));
            assertEquals(-1,ai.get(i));
        }
    }

    /**
     * getAndDecrement returns previous value and decrements
     */
    public void testGetAndDecrement() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertEquals(1,ai.getAndDecrement(i));
            assertEquals(0,ai.getAndDecrement(i));
            assertEquals(-1,ai.getAndDecrement(i));
        }
    }

    /**
     * getAndIncrement returns previous value and increments
     */
    public void testGetAndIncrement() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertEquals(1,ai.getAndIncrement(i));
            assertEquals(2,ai.get(i));
            ai.set(i,-2);
            assertEquals(-2,ai.getAndIncrement(i));
            assertEquals(-1,ai.getAndIncrement(i));
            assertEquals(0,ai.getAndIncrement(i));
            assertEquals(1,ai.get(i));
        }
    }

    /**
     *  addAndGet adds given value to current, and returns current value
     */
    public void testAddAndGet() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertEquals(3,ai.addAndGet(i,2));
            assertEquals(3,ai.get(i));
            assertEquals(-1,ai.addAndGet(i,-4));
            assertEquals(-1,ai.get(i));
        }
    }

    /**
     * decrementAndGet decrements and returns current value
     */
    public void testDecrementAndGet() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertEquals(0,ai.decrementAndGet(i));
            assertEquals(-1,ai.decrementAndGet(i));
            assertEquals(-2,ai.decrementAndGet(i));
            assertEquals(-2,ai.get(i));
        }
    }

    /**
     *  incrementAndGet increments and returns current value
     */
    public void testIncrementAndGet() {
        AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) {
            ai.set(i, 1);
            assertEquals(2,ai.incrementAndGet(i));
            assertEquals(2,ai.get(i));
            ai.set(i, -2);
            assertEquals(-1,ai.incrementAndGet(i));
            assertEquals(0,ai.incrementAndGet(i));
            assertEquals(1,ai.incrementAndGet(i));
            assertEquals(1,ai.get(i));
        }
    }

    static final int COUNTDOWN = 100000;
    
    class Counter implements Runnable {
        final AtomicIntegerArray ai;
        volatile int counts;
        Counter(AtomicIntegerArray a) { ai = a; }
        public void run() {
            for (;;) {
                boolean done = true;
                for (int i = 0; i < ai.length(); ++i) {
                    int v = ai.get(i);
                    threadAssertTrue(v >= 0);
                    if (v != 0) {
                        done = false;
                        if (ai.compareAndSet(i, v, v-1))
                            ++counts;
                    }
                }
                if (done)
                    break;
            }
        }
    }

    /**
     * Multiple threads using same array of counters successfully
     * update a number of times equal to total count
     */
    public void testCountingInMultipleThreads() {
        try {
            final AtomicIntegerArray ai = new AtomicIntegerArray(SIZE); 
            for (int i = 0; i < SIZE; ++i) 
                ai.set(i, COUNTDOWN);
            Counter c1 = new Counter(ai);
            Counter c2 = new Counter(ai);
            Thread t1 = new Thread(c1);
            Thread t2 = new Thread(c2);
            t1.start();
            t2.start();
            t1.join();
            t2.join();
            assertEquals(c1.counts+c2.counts, SIZE * COUNTDOWN);
        }
        catch(InterruptedException ie) {
            unexpectedException();
        }
    }


    /**
     * a deserialized serialized array holds same values
     */
    public void testSerialization() {
        AtomicIntegerArray l = new AtomicIntegerArray(SIZE); 
        for (int i = 0; i < SIZE; ++i) 
            l.set(i, -i);

        try {
            ByteArrayOutputStream bout = new ByteArrayOutputStream(10000);
            ObjectOutputStream out = new ObjectOutputStream(new BufferedOutputStream(bout));
            out.writeObject(l);
            out.close();

            ByteArrayInputStream bin = new ByteArrayInputStream(bout.toByteArray());
            ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(bin));
            AtomicIntegerArray r = (AtomicIntegerArray) in.readObject();
            for (int i = 0; i < SIZE; ++i) {
                assertEquals(l.get(i), r.get(i));
            }
        } catch(Exception e){
            e.printStackTrace();
            unexpectedException();
        }
    }


    /**
     * toString returns current value.
     */ 
    public void testToString() {
        int[] a = { 17, 3, -42, 99, -7};
        AtomicIntegerArray ai = new AtomicIntegerArray(a);
        assertEquals(Arrays.toString(a), ai.toString());
    }

}