Java example source code file (QNameMap.java)

This example Java source code file (QNameMap.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

default_load_factor, entry, entryiterator, entryset, hashiterator, maximum_capacity, object, override, qnamemap, set, string, stringbuilder, unsupportedoperationexception, util

The QNameMap.java Java example source code

/*
 * Copyright (c) 1997, 2011, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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.
 */

package com.sun.xml.internal.bind.v2.util;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.Map;
import java.util.Collection;
import java.util.HashSet;

import javax.xml.namespace.QName;

import com.sun.xml.internal.bind.v2.runtime.Name;

/**
 * Map keyed by {@link QName}.
 *
 * This specialized map allows a look up operation without constructing
 * a new QName instance, for a performance reason. This {@link Map} assumes
 * that both namespace URI and local name are {@link String#intern() intern}ed.
 *
 * @since JAXB 2.0
 */
public final class QNameMap<V> {
    /**
     * The default initial capacity - MUST be a power of two.
     */
    private static final int DEFAULT_INITIAL_CAPACITY = 16;

    /**
     * The maximum capacity, used if a higher value is implicitly specified
     * by either of the constructors with arguments.
     * MUST be a power of two <= 1<<30.
     */
    private static final int MAXIMUM_CAPACITY = 1 << 30;

    /**
     * The table, resized as necessary. Length MUST Always be a power of two.
     */
    transient Entry<V>[] table = new Entry[DEFAULT_INITIAL_CAPACITY];

    /**
     * The number of key-value mappings contained in this identity hash map.
     */
    transient int size;

    /**
     * The next size value at which to resize . Taking it as
     * MAXIMUM_CAPACITY
     * @serial
     */
    private int threshold;

    /**
     * The load factor used when none specified in constructor.
     **/
    private static final float DEFAULT_LOAD_FACTOR = 0.75f;



    /**
     * Gives an entrySet view of this map
     */
    private Set<Entry entrySet = null;

    public QNameMap() {
        threshold = (int)(DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
        table = new Entry[DEFAULT_INITIAL_CAPACITY];

    }

    /**
     * Associates the specified value with the specified keys in this map.
     * If the map previously contained a mapping for this key, the old
     * value is replaced.
     *
     * @param namespaceUri First key with which the specified value is to be associated.
     * @param localname Second key with which the specified value is to be associated.
     * @param value value to be associated with the specified key.
     *
     */
    public void put(String namespaceUri,String localname, V value ) {
        //keys cannot be null
        assert localname !=null;
        assert namespaceUri !=null;
        // keys must be interned
        assert localname == localname.intern();
        assert namespaceUri == namespaceUri.intern();

        int hash = hash(localname);
        int i = indexFor(hash, table.length);

        for (Entry<V> e = table[i]; e != null; e = e.next) {
            if (e.hash == hash && localname == e.localName && namespaceUri==e.nsUri) {
                e.value = value;
                return;
            }
        }

        addEntry(hash, namespaceUri,localname, value, i);

    }

    public void put(QName name, V value ) {
        put(name.getNamespaceURI(),name.getLocalPart(),value);
    }

    public void put(Name name, V value ) {
        put(name.nsUri,name.localName,value);
    }

    /**
     * Returns the value to which the specified keys are mapped in this QNameMap,
     * or <tt>null if the map contains no mapping for this key.
     *
     * @param   nsUri the namespaceUri key whose associated value is to be returned.
     * @param   localPart the localPart key whose associated value is to be returned.
     * @return  the value to which this map maps the specified set of keya, or
     *          <tt>null if the map contains no mapping for this set of keys.
     * @see #put(String,String, Object)
     */
    public V get( String nsUri, String localPart ) {
        Entry<V> e = getEntry(nsUri,localPart);
        if(e==null) return null;
        else        return e.value;
        }

    public V get( QName name ) {
        return get(name.getNamespaceURI(),name.getLocalPart());
    }

    /**
     * Returns the number of keys-value mappings in this map.
     *
     * @return the number of keys-value mappings in this map.
     */
    public int size() {
        return size;
    }

    /**
     * Copies all of the mappings from the specified map to this map
     * These mappings will replace any mappings that
     * this map had for any of the keys currently in the specified map.
     *
     * @param map mappings to be stored in this map.
     *
     */
    public QNameMap<V> putAll(QNameMap map) {
        int numKeysToBeAdded = map.size();
        if (numKeysToBeAdded == 0)
            return this;


        if (numKeysToBeAdded > threshold) {
            int targetCapacity = numKeysToBeAdded;
            if (targetCapacity > MAXIMUM_CAPACITY)
                targetCapacity = MAXIMUM_CAPACITY;
            int newCapacity = table.length;
            while (newCapacity < targetCapacity)
                newCapacity <<= 1;
            if (newCapacity > table.length)
                resize(newCapacity);
        }

        for( Entry<? extends V> e : map.entrySet() )
            put(e.nsUri,e.localName,e.getValue());
        return this;
    }


    /**
     * Returns a hash value for the specified object.The hash value is computed
     * for the localName.
     */
    private static int hash(String x) {
        int h = x.hashCode();

        h += ~(h << 9);
        h ^=  (h >>> 14);
        h +=  (h << 4);
        h ^=  (h >>> 10);
        return h;
    }

    /**
     * Returns index for hash code h.
     */
    private static int indexFor(int h, int length) {
        return h & (length-1);
    }

    /**
     * Add a new entry with the specified keys, value and hash code to
     * the specified bucket.  It is the responsibility of this
     * method to resize the table if appropriate.
     *
     */
    private void addEntry(int hash, String nsUri, String localName, V value, int bucketIndex) {
        Entry<V> e = table[bucketIndex];
        table[bucketIndex] = new Entry<V>(hash, nsUri, localName, value, e);
        if (size++ >= threshold)
            resize(2 * table.length);
    }


    /**
     * Rehashes the contents of this map into a new array with a
     * larger capacity.  This method is called automatically when the
     * number of keys in this map reaches its threshold.
     */
    private void resize(int newCapacity) {
        Entry[] oldTable = table;
        int oldCapacity = oldTable.length;
        if (oldCapacity == MAXIMUM_CAPACITY) {
            threshold = Integer.MAX_VALUE;
            return;
        }

        Entry[] newTable = new Entry[newCapacity];
        transfer(newTable);
        table = newTable;
        threshold = newCapacity;
    }

    /**
     * Transfer all entries from current table to newTable.
     */
    private void transfer(Entry<V>[] newTable) {
        Entry<V>[] src = table;
        int newCapacity = newTable.length;
        for (int j = 0; j < src.length; j++) {
            Entry<V> e = src[j];
            if (e != null) {
                src[j] = null;
                do {
                    Entry<V> next = e.next;
                    int i = indexFor(e.hash, newCapacity);
                    e.next = newTable[i];
                    newTable[i] = e;
                    e = next;
                } while (e != null);
            }
        }
    }

    /**
     * Returns one random item in the map.
     * If this map is empty, return null.
     *
     * <p>
     * This method is useful to obtain the value from a map that only contains one element.
     */
    public Entry<V> getOne() {
        for( Entry<V> e : table ) {
            if(e!=null)
                return e;
        }
        return null;
    }

    public Collection<QName> keySet() {
        Set<QName> r = new HashSet();
        for (Entry<V> e : entrySet()) {
            r.add(e.createQName());
        }
        return r;
    }

    private abstract class HashIterator<E> implements Iterator {
        Entry<V> next;  // next entry to return
        int index;              // current slot

        HashIterator() {
            Entry<V>[] t = table;
            int i = t.length;
            Entry<V> n = null;
            if (size != 0) { // advance to first entry
                while (i > 0 && (n = t[--i]) == null) {}
            }
            next = n;
            index = i;
        }

        public boolean hasNext() {
            return next != null;
        }

        Entry<V> nextEntry() {
            Entry<V> e = next;
            if (e == null)
                throw new NoSuchElementException();

            Entry<V> n = e.next;
            Entry<V>[] t = table;
            int i = index;
            while (n == null && i > 0)
                n = t[--i];
            index = i;
            next = n;
            return e;
        }

        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

    public boolean containsKey(String nsUri,String localName) {
        return getEntry(nsUri,localName)!=null;
    }


    /**
     * Returns true if this map is empty.
     */
    public boolean isEmpty() {
        return size == 0;
    }


    public static final class Entry<V>  {
        /** The namespace URI. */
        public final String nsUri;

        /** The localPart. */
        public final String localName;

        V value;
        final int hash;
        Entry<V> next;

        /**
         * Create new entry.
         */
        Entry(int h, String nsUri, String localName, V v, Entry<V> n) {
            value = v;
            next = n;
            this.nsUri = nsUri;
            this.localName = localName;
            hash = h;
        }

        /**
         * Creates a new QName object from {@link #nsUri} and {@link #localName}.
         */
        public QName createQName() {
            return new QName(nsUri,localName);
        }

        public V getValue() {
            return value;
        }

        public V setValue(V newValue) {
            V oldValue = value;
            value = newValue;
            return oldValue;
        }

        @Override
        public boolean equals(Object o) {
            if (!(o instanceof Entry))
                return false;
            Entry e = (Entry)o;
            String k1 = nsUri;
            String k2 = e.nsUri;
            String k3 = localName;
            String k4 = e.localName;
            if (k1 == k2 || (k1 != null && k1.equals(k2)) &&
                    (k3 == k4 ||(k3 !=null && k3.equals(k4)))) {
                Object v1 = getValue();
                Object v2 = e.getValue();
                if (v1 == v2 || (v1 != null && v1.equals(v2)))
                    return true;
            }
            return false;
        }

        @Override
        public int hashCode() {
            return ( localName.hashCode()) ^
                    (value==null   ? 0 : value.hashCode());
        }

        @Override
        public String toString() {
            return '"'+nsUri +"\",\"" +localName + "\"=" + getValue();
        }
    }

    public Set<Entry entrySet() {
        Set<Entry es = entrySet;
        return es != null ? es : (entrySet = new EntrySet());
    }

    private Iterator<Entry newEntryIterator() {
        return new EntryIterator();
    }

    private class EntryIterator extends HashIterator<Entry {
        public Entry<V> next() {
            return nextEntry();
        }
    }
    private class EntrySet extends AbstractSet<Entry {
        public Iterator<Entry iterator() {
            return newEntryIterator();
        }
        @Override
        public boolean contains(Object o) {
            if (!(o instanceof Entry))
                return false;
            Entry<V> e = (Entry) o;
            Entry<V> candidate = getEntry(e.nsUri,e.localName);
            return candidate != null && candidate.equals(e);
        }
        @Override
        public boolean remove(Object o) {
            throw new UnsupportedOperationException();
        }
        public int size() {
            return size;
        }
    }

    private Entry<V> getEntry(String nsUri,String localName) {
        // strings must be interned
        assert nsUri==nsUri.intern();
        assert localName==localName.intern();

        int hash = hash(localName);
        int i = indexFor(hash, table.length);
        Entry<V> e = table[i];
        while (e != null && !(localName == e.localName && nsUri == e.nsUri))
            e = e.next;
        return e;
    }

    @Override
    public String toString() {
        StringBuilder buf = new StringBuilder();
        buf.append('{');

        for( Entry<V> e : entrySet() ) {
            if(buf.length()>1)
                buf.append(',');
            buf.append('[');
            buf.append(e);
            buf.append(']');
        }

        buf.append('}');
        return buf.toString();
    }
}