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Java example source code file (ToArrayTest.java)

This example Java source code file (ToArrayTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractcollection, arraystoreexception, candidate, cap, exception, iterator, not, object, override, string, testcollection, throwable, toarraytest, unsupportedoperationexception, util

The ToArrayTest.java Java example source code

/*
 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * 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).
 *
 * You should have received a copy of the GNU General Public License version
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * @test
 * @bug 7121314
 * @summary AbstractCollection.toArray(T[]) doesn't return the given array
 *           in concurrent modification.
 * @author Ulf Zibis, David Holmes
 */

import java.util.AbstractCollection;
import java.util.Arrays;
import java.util.Iterator;

public class ToArrayTest {

    static class TestCollection<E> extends AbstractCollection {
        private final E[] elements;
        private int[] sizes;
        private int nextSize;

        public TestCollection(E[] elements) {
            this.elements = elements;
            setSizeSequence(new int[] { elements.length });
        }

        /*
         * Sets the values that size() will return on each use. The next
         * call to size will return sizes[0], then sizes[1] etc. This allows us
         * to emulate a concurrent change to the contents of the collection
         * without having to perform concurrent changes. If sizes[n+1] contains
         * a larger value, the collection will appear to have shrunk when
         * iterated; if a smaller value then the collection will appear to have
         * grown when iterated.
         */
        void setSizeSequence(int... sizes) {
            this.sizes = sizes;
            nextSize = 0;
        }

        /* can change collection's size after each invocation */
        @Override
        public int size() {
            return sizes[nextSize == sizes.length - 1 ? nextSize : nextSize++];
        }

        @Override
        public Iterator<E> iterator() {
            return new Iterator<E>() {
                int pos = 0;

                public boolean hasNext() {
                    return pos < sizes[nextSize];
                }
                public E next() {
                    return elements[pos++];
                }
                public void remove() {
                    throw new UnsupportedOperationException(
                            "Not supported yet.");
                }
            };
        }
    }

    static final Object[] OBJECTS = { new Object(), new Object(), new Object() };
    static final TestCollection<?> CANDIDATE = new TestCollection(OBJECTS);
    static final int CAP = OBJECTS.length; // capacity of the CANDIDATE
    static final int LAST = CAP - 1; // last possible array index
    Object[] a;
    Object[] res;

    int last() {
        return a.length - 1;
    }

    protected void test() throws Throwable {
        // Check array type conversion
        res = new TestCollection<>(new Object[] { "1", "2" }).toArray(new String[0]);
        check(res instanceof String[]);
        check(res.length == 2);
        check(res[1] == "2");

        // Check incompatible type of target array
        try {
            res = CANDIDATE.toArray(new String[CAP]);
            check(false);
        } catch (Throwable t) {
            check(t instanceof ArrayStoreException);
        }

        // Check more elements than a.length
        a = new Object[CAP - 1]; // appears too small
        res = CANDIDATE.toArray(a);
        check(res != a);
        check(res[LAST] != null);

        // Check equal elements as a.length
        a = new Object[CAP]; // appears to match
        res = CANDIDATE.toArray(a);
        check(res == a);
        check(res[last()] != null);

        // Check equal elements as a.length
        a = new Object[CAP + 1]; // appears too big
        res = CANDIDATE.toArray(a);
        check(res == a);
        check(res[last()] == null);

        // Check less elements than expected, but more than a.length
        a = new Object[CAP - 2]; // appears too small
        CANDIDATE.setSizeSequence(CAP, CAP - 1);
        res = CANDIDATE.toArray(a);
        check(res != a);
        check(res.length == CAP - 1);
        check(res[LAST - 1] != null);

        // Check less elements than expected, but equal as a.length
        a = Arrays.copyOf(OBJECTS, CAP); // appears to match
        CANDIDATE.setSizeSequence(CAP, CAP - 1);
        res = CANDIDATE.toArray(a);
        check(res == a);
        check(res[last()] == null);

        // Check more elements than expected and more than a.length
        a = new Object[CAP - 1]; // appears to match
        CANDIDATE.setSizeSequence(CAP - 1, CAP);
        res = CANDIDATE.toArray(a);
        check(res != a);
        check(res[LAST] != null);

        // Check more elements than expected, but equal as a.length
        a = new Object[CAP - 1]; // appears to match
        CANDIDATE.setSizeSequence(CAP - 2, CAP - 1);
        res = CANDIDATE.toArray(a);
        check(res == a);
        check(res[last()] != null);

        // Check more elements than expected, but less than a.length
        a = Arrays.copyOf(OBJECTS, CAP); // appears to match
        CANDIDATE.setSizeSequence(CAP - 2, CAP - 1);
        res = CANDIDATE.toArray(a);
        check(res == a);
        check(res[last()] == null);

        test_7121314();
    }

    /*
     * Major target of this testcase, bug 7121314.
     */
    protected void test_7121314() throws Throwable {
        // Check equal elements as a.length, but less than expected
        a = new Object[CAP - 1]; // appears too small
        CANDIDATE.setSizeSequence(CAP, CAP - 1);
        res = CANDIDATE.toArray(a);
        check(res == a);
        check(res[last()] != null);

        // Check less elements than a.length and less than expected
        a = Arrays.copyOf(OBJECTS, CAP - 1); // appears too small
        CANDIDATE.setSizeSequence(CAP, CAP - 2);
        res = CANDIDATE.toArray(a);
        check(res == a);
        check(res[last()] == null);

    }

    public static void main(String[] args) throws Throwable {
        ToArrayTest testcase = new ToArrayTest();
        try {
            testcase.test();
        } catch (Throwable t) {
            unexpected(t);
        }

        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
        if (failed > 0) throw new Exception("Some tests failed");
    }

    //--------------------- Infrastructure ---------------------------
    static volatile int passed = 0, failed = 0;
    static void pass() { passed++; }
    static void fail() { failed++; Thread.dumpStack(); }
    static void fail(String msg) { System.out.println(msg); fail(); }
    static void unexpected(Throwable t) { failed++; t.printStackTrace(); }
    static void check(boolean cond) { if (cond) pass(); else fail(); }
    static void equal(Object x, Object y) {
        if (x == null ? y == null : x.equals(y)) pass();
        else {System.out.println(x + " not equal to " + y); fail(); }
    }
}






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