modules/concurrent/src/test/java/AtomicReferenceTest.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.*;

public class AtomicReferenceTest extends JSR166TestCase {
    public static void main (String[] args) {
        junit.textui.TestRunner.run (suite());
    }
    public static Test suite() {
        return new TestSuite(AtomicReferenceTest.class);
    }

    /**
     * constructor initializes to given value
     */
    public void testConstructor(){
        AtomicReference ai = new AtomicReference(one);
	assertEquals(one,ai.get());
    }

    /**
     * default constructed initializes to null
     */
    public void testConstructor2(){
        AtomicReference ai = new AtomicReference();
	assertNull(ai.get());
    }

    /**
     * get returns the last value set
     */
    public void testGetSet(){
        AtomicReference ai = new AtomicReference(one);
	assertEquals(one,ai.get());
	ai.set(two);
	assertEquals(two,ai.get());
	ai.set(m3);
	assertEquals(m3,ai.get());

    }
    /**
     * compareAndSet succeeds in changing value if equal to expected else fails
     */
    public void testCompareAndSet(){
        AtomicReference ai = new AtomicReference(one);
	assertTrue(ai.compareAndSet(one,two));
	assertTrue(ai.compareAndSet(two,m4));
	assertEquals(m4,ai.get());
	assertFalse(ai.compareAndSet(m5,seven));
	assertFalse((seven.equals(ai.get())));
	assertTrue(ai.compareAndSet(m4,seven));
	assertEquals(seven,ai.get());
    }

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

    /**
     * repeated weakCompareAndSet succeeds in changing value when equal
     * to expected 
     */
    public void testWeakCompareAndSet(){
        AtomicReference ai = new AtomicReference(one);
	while(!ai.weakCompareAndSet(one,two));
	while(!ai.weakCompareAndSet(two,m4));
	assertEquals(m4,ai.get());
        while(!ai.weakCompareAndSet(m4,seven));
	assertEquals(seven,ai.get());
    }

    /**
     * getAndSet returns previous value and sets to given value
     */
    public void testGetAndSet(){
        AtomicReference ai = new AtomicReference(one);
	assertEquals(one,ai.getAndSet(zero));
	assertEquals(zero,ai.getAndSet(m10));
	assertEquals(m10,ai.getAndSet(one));
    }

    /**
     * a deserialized serialized atomic holds same value
     */
    public void testSerialization() {
        AtomicReference l = new AtomicReference();

        try {
            l.set(one);
            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));
            AtomicReference r = (AtomicReference) in.readObject();
            assertEquals(l.get(), r.get());
        } catch(Exception e){
            unexpectedException();
        }
    }

    /**
     * toString returns current value.
     */ 
    public void testToString() {
        AtomicReference<Integer> ai = new AtomicReference<Integer>(one); 
        assertEquals(ai.toString(), one.toString());
        ai.set(two);
        assertEquals(ai.toString(), two.toString());
    }

}