HSQLDB example source code file (HsqlArrayHeap.java)

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

Java - HSQLDB tags/keywords

exception, hsqlarrayheap, hsqlarrayheap, hsqlheap, illegalargumentexception, illegalargumentexception, object, object, objectcomparator, runtimeexception, string, stringbuffer, stringbuffer

The HSQLDB HsqlArrayHeap.java source code

/* Copyright (c) 2001-2008, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


package org.hsqldb.lib;

/**
 * An HsqlHeap implementation backed by an array of objects and an
 * {@link ObjectComparator ObjectComparator}.  This implementation
 * is non-blocking, dynamically resizing and thread-safe.
 *
 * @author boucherb@users
 * @version 1.7.2
 * @since 1.7.2
 */
public class HsqlArrayHeap implements HsqlHeap {

// --------------------------------- members -----------------------------------
    protected ObjectComparator oc;
    protected int              count;
    protected Object[]         heap;

// ------------------------------ constructors ---------------------------------

    /**
     * Creates a new HsqlArrayHeap with the given initial capacity, using
     * the specified ObjectComparator to maintain the heap invariant.
     *
     * @exception IllegalArgumentException if capacity less or equal to zero
     *      or comparator is null
     */
    public HsqlArrayHeap(int capacity,
                         ObjectComparator comparator)
                         throws IllegalArgumentException {

        if (capacity <= 0) {
            throw new IllegalArgumentException("" + capacity);
        }

        if (comparator == null) {
            throw new IllegalArgumentException("null comparator");
        }

        heap = new Object[capacity];
        oc   = comparator;
    }

//    /** Copy constructor (optional) */
//    public HsqlArrayHeap(HsqlArrayHeap other) {
//        count = other.count;
//        oc    = other.oc;
//        heap  = new Object[count];
//        System.arraycopy(other.heap,0, heap, 0, count);
//    }
// -------------------------- interface Implementation -------------------------
    public synchronized void clear() {

        for (int i = 0; i < count; ++i) {
            heap[i] = null;
        }

        count = 0;
    }

    public synchronized void add(Object o)
    throws IllegalArgumentException, RuntimeException {

        int ci;    // current index
        int pi;    // parent index

        if (o == null) {
            throw new IllegalArgumentException("null element");
        }

        if (isFull()) {
            throw new RuntimeException("full");
        }

        if (count >= heap.length) {
            increaseCapacity();
        }

        ci = count;

        count++;

        do {
            if (ci <= 0) {
                break;
            }

            pi = (ci - 1) >> 1;

            try {
                if (oc.compare(o, heap[pi]) >= 0) {
                    break;
                }
            } catch (Exception e) {
                throw new IllegalArgumentException(e.toString());
            }

            heap[ci] = heap[pi];
            ci       = pi;
        } while (true);

        heap[ci] = o;
    }

    public synchronized boolean isEmpty() {
        return count == 0;
    }

    public synchronized boolean isFull() {

        // almost impossible for this to happen
        return count == Integer.MAX_VALUE;
    }

    public synchronized Object peek() {
        return heap[0];
    }

    public synchronized Object remove() {

        int    ci;     // current index
        int    li;     // left index
        int    ri;     // right index
        int    chi;    // child index
        Object co;
        Object ro;

        if (count == 0) {
            return null;
        }

        ci = 0;
        ro = heap[ci];

        count--;

        if (count == 0) {
            heap[0] = null;

            return ro;
        }

        co          = heap[count];
        heap[count] = null;

        do {
            li = (ci << 1) + 1;

            if (li >= count) {
                break;
            }

            ri  = (ci << 1) + 2;
            chi = (ri >= count || oc.compare(heap[li], heap[ri]) < 0) ? li
                                                                      : ri;

            if (oc.compare(co, heap[chi]) <= 0) {
                break;
            }

            heap[ci] = heap[chi];
            ci       = chi;
        } while (true);

        heap[ci] = co;

        return ro;
    }

    public synchronized int size() {
        return count;
    }

// ------------- standard object and collection methods (optional) -------------
//    public synchronized Object clone() throws CloneNotSupportedException {
//        return new HsqlArrayHeap(this);
//    }
//
//    public synchronized java.util.Enumeration elements() {
//
//        Object[] elements;
//
//        elements = new Object[count];
//
//        System.arraycopy(heap, 0, elements, 0, count);
//
//        return new HsqlEnumeration(elements);
//    }
//
//    public synchronized boolean equals(Object o) {
//
//        HsqlArrayHeap other;
//        HsqlArrayHeap thiscopy;
//        HsqlArrayHeap othercopy;
//
//        if (this == o) {
//            return true;
//        }
//
//        if (!(o instanceof HsqlArrayHeap)) {
//            return false;
//        }
//
//        other = (HsqlArrayHeap) o;
//
//        if (count != other.size()) {
//            return false;
//        }
//
//        // this is a bit "iffy"... non-equal comparators _might_ still
//        // be _equivalent_ under current element content...
//
//        if (!oc.equals(other.oc)) {
//            return false;
//        }
//
//        thiscopy = new HsqlArrayHeap(this);
//        othercopy = new HsqlArrayHeap(other);
//
//        while(!thiscopy.isEmpty()) {
//            if (!thiscopy.remove().equals(othercopy.remove())) {
//                return false;
//            }
//        }
//
//        return true;
//    }
//
//    public synchronized Object[] toArray(Object a[]) {
//
//        if (a == null) {
//            a = new Object[count];
//        } else if ( a.length < count) {
//            a = (Object[]) java.lang.reflect.Array.newInstance(
//                a.getClass().getComponentType(), count);
//        }
//
//        System.arraycopy(heap, 0, a, 0, count);
//
//        for (int i = count; i < a.length; i++) {
//            a[i] = null;
//        }
//
//        return a;
//    }
//
    public synchronized String toString() {

        StringBuffer sb = new StringBuffer();

        sb.append(super.toString());
        sb.append(" : size=");
        sb.append(count);
        sb.append(' ');
        sb.append('[');

        for (int i = 0; i < count; i++) {
            sb.append(heap[i]);

            if (i + 1 < count) {
                sb.append(',');
                sb.append(' ');
            }
        }

        sb.append(']');

        return sb.toString();
    }

//
//    public void trim() {
//
//        Object[] oldheap;
//
//        oldheap = heap;
//
//        heap = new Object[count == 0 ? 16 : count];
//
//        System.arraycopy(oldheap, 0, heap, 0, count);
//    }
// -------------------- internal implementation methods ------------------------
    private void increaseCapacity() {

        Object[] oldheap;

        // no handling of boundary conditions.
        // In the highly unlikely event of a rollover,
        // in theory, an exception will be thrown (negative array index in
        // array allocation?)
        oldheap = heap;

        // as per java collections, v.s. JDK 1.1 java util.
        heap = new Object[3 * heap.length / 2 + 1];

        System.arraycopy(oldheap, 0, heap, 0, count);
    }
}