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*
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
/*
* @test
* @bug 8146568
* @summary brittle white box test of internal array management
* @modules java.base/java.util:open
* @run testng ArrayManagement
*/
import java.lang.reflect.Field;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.SplittableRandom;
import org.testng.annotations.Test;
import static org.testng.Assert.*;
public class ArrayManagement {
static final int DEFAULT_CAPACITY = 10;
static final Field ELEMENT_DATA;
static final Field MODCOUNT;
static final SplittableRandom rnd = new SplittableRandom();
static {
try {
ELEMENT_DATA = ArrayList.class.getDeclaredField("elementData");
ELEMENT_DATA.setAccessible(true);
MODCOUNT = AbstractList.class.getDeclaredField("modCount");
MODCOUNT.setAccessible(true);
} catch (ReflectiveOperationException huh) {
throw new AssertionError(huh);
}
}
static Object[] elementData(ArrayList<?> list) {
try {
return (Object[]) ELEMENT_DATA.get(list);
} catch (ReflectiveOperationException huh) {
throw new AssertionError(huh);
}
}
static int modCount(ArrayList<?> list) {
try {
return MODCOUNT.getInt(list);
} catch (ReflectiveOperationException huh) {
throw new AssertionError(huh);
}
}
static int capacity(ArrayList<?> list) {
return elementData(list).length;
}
static int newCapacity(int oldCapacity) {
return oldCapacity + (oldCapacity >> 1);
}
static void ensureCapacity(ArrayList<Object> list, int capacity) {
int oldCapacity = capacity(list);
int oldModCount = modCount(list);
list.ensureCapacity(capacity);
assertTrue(capacity(list) >= capacity || capacity(list) == 0);
assertEquals(modCount(list),
(capacity(list) == oldCapacity)
? oldModCount
: oldModCount + 1);
}
static List<Object> singletonList() {
return Collections.singletonList(Boolean.TRUE);
}
/** Opportunistically randomly test various add operations. */
static void addOneElement(ArrayList<Object> list) {
int size = list.size();
int modCount = modCount(list);
switch (rnd.nextInt(4)) {
case 0: assertTrue(list.add(Boolean.TRUE)); break;
case 1: list.add(size, Boolean.TRUE); break;
case 2: assertTrue(list.addAll(singletonList())); break;
case 3: assertTrue(list.addAll(size, singletonList())); break;
default: throw new AssertionError();
}
assertEquals(modCount(list), modCount + 1);
assertEquals(list.size(), size + 1);
}
@Test public void defaultCapacity() {
ArrayList<Object> list = new ArrayList<>();
assertEquals(capacity(new ArrayList<Object>()), 0);
for (int i = 0; i < DEFAULT_CAPACITY; i++) {
addOneElement(list);
assertEquals(capacity(list), DEFAULT_CAPACITY);
}
addOneElement(list);
assertEquals(capacity(list), newCapacity(DEFAULT_CAPACITY));
}
@Test public void defaultCapacityEnsureCapacity() {
ArrayList<Object> list = new ArrayList<>();
for (int i = 0; i <= DEFAULT_CAPACITY; i++) {
ensureCapacity(list, i); // no-op!
assertEquals(capacity(list), 0);
}
for (int i = 0; i < DEFAULT_CAPACITY; i++) {
addOneElement(list);
assertEquals(capacity(list), DEFAULT_CAPACITY);
}
addOneElement(list);
assertEquals(capacity(list), newCapacity(DEFAULT_CAPACITY));
{
int capacity = capacity(list);
ensureCapacity(list, capacity + 1);
assertEquals(capacity(list), newCapacity(capacity));
}
{
int capacity = capacity(list);
ensureCapacity(list, 3 * capacity);
assertEquals(capacity(list), 3 * capacity);
}
}
@Test public void ensureCapacityBeyondDefaultCapacity() {
ArrayList<Object> list = new ArrayList<>();
list.ensureCapacity(DEFAULT_CAPACITY + 1);
assertEquals(capacity(list), DEFAULT_CAPACITY + 1);
for (int i = 0; i < DEFAULT_CAPACITY + 1; i++) {
addOneElement(list);
assertEquals(capacity(list), DEFAULT_CAPACITY + 1);
}
addOneElement(list);
assertEquals(capacity(list), newCapacity(DEFAULT_CAPACITY + 1));
}
@Test public void explicitZeroCapacity() {
ArrayList<Object> list = new ArrayList<>(0);
assertEquals(capacity(list), 0);
addOneElement(list);
assertEquals(capacity(list), 1);
addOneElement(list);
assertEquals(capacity(list), 2);
addOneElement(list);
assertEquals(capacity(list), 3);
addOneElement(list);
assertEquals(capacity(list), 4);
addOneElement(list);
assertEquals(capacity(list), 6);
addOneElement(list);
assertEquals(capacity(list), 6);
addOneElement(list);
assertEquals(capacity(list), 9);
list.clear();
assertEquals(capacity(list), 9);
}
@Test public void explicitLargeCapacity() {
int n = DEFAULT_CAPACITY * 3;
ArrayList<Object> list = new ArrayList<>(n);
assertEquals(capacity(list), n);
ensureCapacity(list, 0);
ensureCapacity(list, n);
for (int i = 0; i < n; i++) addOneElement(list);
assertEquals(capacity(list), n);
addOneElement(list);
assertEquals(capacity(list), newCapacity(n));
}
@Test public void emptyArraysAreShared() {
assertSame(elementData(new ArrayList<Object>()),
elementData(new ArrayList<Object>()));
assertSame(elementData(new ArrayList<Object>(0)),
elementData(new ArrayList<Object>(0)));
}
@Test public void emptyArraysDifferBetweenDefaultAndExplicit() {
assertNotSame(elementData(new ArrayList<Object>()),
elementData(new ArrayList<Object>(0)));
}
@Test public void negativeCapacity() {
for (int capacity : new int[] { -1, Integer.MIN_VALUE }) {
try {
new ArrayList<Object>(capacity);
fail("should throw");
} catch (IllegalArgumentException success) {}
}
}
}