PreviousBits.java

/*
 * Copyright (c) 2007, 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 6410729 6586631
 * @summary Test previousClearBit, previousSetBit
 * @key randomness
 */

import java.util.*;

public class PreviousBits {

    void testHashCode(final BitSet s) {
        long h = 1234;
        long[] words = s.toLongArray();
        for (int i = words.length; --i >= 0; )
            h ^= words[i] * (i + 1);
        equal((int)((h >> 32) ^ h), s.hashCode());
    }

    void testOutOfBounds(final BitSet s) {
        THROWS(IndexOutOfBoundsException.class,
               new F(){void f(){ s.previousSetBit(-2);}},
               new F(){void f(){ s.previousClearBit(-2);}},
               new F(){void f(){ s.previousSetBit(Integer.MIN_VALUE);}},
               new F(){void f(){ s.previousClearBit(Integer.MIN_VALUE);}},
               new F(){void f(){ s.nextSetBit(-1);}},
               new F(){void f(){ s.nextClearBit(-1);}},
               new F(){void f(){ s.nextSetBit(Integer.MIN_VALUE);}},
               new F(){void f(){ s.nextClearBit(Integer.MIN_VALUE);}});
    }

    void test(String[] args) throws Throwable {
        final BitSet s = new BitSet();

        // Test empty bitset
        testOutOfBounds(s);
        testHashCode(s);

        for (int i = -1; i < 93;) {
            equal(-1, s.previousSetBit(i));
            equal( i, s.previousClearBit(i));
            i++;
            equal(-1, s.nextSetBit(i));
            equal( i, s.nextClearBit(i));
        }

        // Test "singleton" bitsets
        for (int j = 0; j < 161; j++) {
            s.clear();
            s.set(j);
            testOutOfBounds(s);
            testHashCode(s);

            for (int i = -1; i < j; i++) {
                equal(-1, s.previousSetBit(i));
                equal( i, s.previousClearBit(i));
                if (i >= 0) {
                    equal(j, s.nextSetBit(i));
                    equal(i, s.nextClearBit(i));
                }
            }

            equal(j,   s.previousSetBit(j));
            equal(j-1, s.previousClearBit(j));
            equal(j,   s.nextSetBit(j));
            equal(j+1, s.nextClearBit(j));

            for (int i = j+1; i < j+100; i++) {
                equal(j, s.previousSetBit(i));
                equal(i, s.previousClearBit(i));
                equal(-1, s.nextSetBit(i));
                equal(i, s.nextClearBit(i));
            }
        }

        // set even bits
        s.clear();
        for (int i = 0; i <= 128; i+=2)
            s.set(i);
        testHashCode(s);
        for (int i = 1; i <= 128; i++) {
            equal(s.previousSetBit(i),
                  ((i & 1) == 0) ? i : i - 1);
            equal(s.previousClearBit(i),
                  ((i & 1) == 0) ? i - 1 : i);
        }

        // set odd bits as well
        for (int i = 1; i <= 128; i+=2)
            s.set(i);
        testHashCode(s);
        for (int i = 1; i <= 128; i++) {
            equal(s.previousSetBit(i), i);
            equal(s.previousClearBit(i), -1);
        }

        // Test loops documented in javadoc
        Random rnd = new Random();
        s.clear();
        for (int i = 0; i < 10; i++)
            s.set(rnd.nextInt(1066));
        List<Integer> down = new ArrayList<Integer>();
        for (int i = s.length(); (i = s.previousSetBit(i-1)) >= 0; )
            down.add(i);
        List<Integer> up = new ArrayList<Integer>();
        for (int i = s.nextSetBit(0); i >= 0; i = s.nextSetBit(i+1))
            up.add(i);
        Collections.reverse(up);
        equal(up, down);
    }

    //--------------------- Infrastructure ---------------------------
    volatile int passed = 0, failed = 0;
    void pass() {passed++;}
    void fail() {failed++; Thread.dumpStack();}
    void fail(String msg) {System.err.println(msg); fail();}
    void unexpected(Throwable t) {failed++; t.printStackTrace();}
    void check(boolean cond) {if (cond) pass(); else fail();}
    void equal(Object x, Object y) {
        if (x == null ? y == null : x.equals(y)) pass();
        else fail(x + " not equal to " + y);}
    public static void main(String[] args) throws Throwable {
        new PreviousBits().instanceMain(args);}
    void instanceMain(String[] args) throws Throwable {
        try {test(args);} catch (Throwable t) {unexpected(t);}
        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
        if (failed > 0) throw new AssertionError("Some tests failed");}
    abstract class F {abstract void f() throws Throwable;}
    void THROWS(Class<? extends Throwable> k, F... fs) {
        for (F f : fs)
            try {f.f(); fail("Expected " + k.getName() + " not thrown");}
            catch (Throwable t) {
                if (k.isAssignableFrom(t.getClass())) pass();
                else unexpected(t);}}
}