289 lines
9.7 KiB
Java
289 lines
9.7 KiB
Java
/*
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* Copyright (c) 2004, 2012, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.util;
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import java.util.Iterator;
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import java.util.Map;
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import java.util.Set;
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import java.util.AbstractMap;
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import java.util.AbstractSet;
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import java.util.NoSuchElementException;
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/**
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* A precomputed hash map.
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*
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* <p> Subclasses of this class are of the following form:
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*
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* <blockquote><pre>
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* class FooMap
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* extends sun.util.PreHashedMap<String>
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* {
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*
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* private FooMap() {
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* super(ROWS, SIZE, SHIFT, MASK);
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* }
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*
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* protected void init(Object[] ht) {
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* ht[0] = new Object[] { "key-1", value_1 };
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* ht[1] = new Object[] { "key-2", value_2,
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* new Object { "key-3", value_3 } };
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* ...
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* }
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*
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* }</pre></blockquote>
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*
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* <p> The <tt>init</tt> method is invoked by the <tt>PreHashedMap</tt>
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* constructor with an object array long enough for the map's rows. The method
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* must construct the hash chain for each row and store it in the appropriate
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* element of the array.
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*
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* <p> Each entry in the map is represented by a unique hash-chain node. The
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* final node of a hash chain is a two-element object array whose first element
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* is the entry's key and whose second element is the entry's value. A
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* non-final node of a hash chain is a three-element object array whose first
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* two elements are the entry's key and value and whose third element is the
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* next node in the chain.
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*
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* <p> Instances of this class are mutable and are not safe for concurrent
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* access. They may be made immutable and thread-safe via the appropriate
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* methods in the {@link java.util.Collections} utility class.
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*
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* <p> In the JDK build, subclasses of this class are typically created via the
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* <tt>Hasher</tt> program in the <tt>make/tools/Hasher</tt> directory.
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*
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* @author Mark Reinhold
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* @since 1.5
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*
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* @see java.util.AbstractMap
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*/
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public abstract class PreHashedMap<V>
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extends AbstractMap<String,V>
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{
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private final int rows;
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private final int size;
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private final int shift;
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private final int mask;
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private final Object[] ht;
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/**
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* Creates a new map.
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*
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* <p> This constructor invokes the {@link #init init} method, passing it a
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* newly-constructed row array that is <tt>rows</tt> elements long.
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*
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* @param rows
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* The number of rows in the map
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* @param size
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* The number of entries in the map
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* @param shift
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* The value by which hash codes are right-shifted
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* @param mask
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* The value with which hash codes are masked after being shifted
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*/
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protected PreHashedMap(int rows, int size, int shift, int mask) {
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this.rows = rows;
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this.size = size;
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this.shift = shift;
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this.mask = mask;
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this.ht = new Object[rows];
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init(ht);
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}
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/**
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* Initializes this map.
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*
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* <p> This method must construct the map's hash chains and store them into
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* the appropriate elements of the given hash-table row array.
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*
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* @param rows
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* The row array to be initialized
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*/
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protected abstract void init(Object[] ht);
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@SuppressWarnings("unchecked")
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private V toV(Object x) {
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return (V)x;
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}
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public V get(Object k) {
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int h = (k.hashCode() >> shift) & mask;
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Object[] a = (Object[])ht[h];
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if (a == null) return null;
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for (;;) {
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if (a[0].equals(k))
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return toV(a[1]);
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if (a.length < 3)
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return null;
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a = (Object[])a[2];
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}
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}
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/**
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* @throws UnsupportedOperationException
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* If the given key is not part of this map's initial key set
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*/
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public V put(String k, V v) {
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int h = (k.hashCode() >> shift) & mask;
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Object[] a = (Object[])ht[h];
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if (a == null)
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throw new UnsupportedOperationException(k);
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for (;;) {
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if (a[0].equals(k)) {
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V ov = toV(a[1]);
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a[1] = v;
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return ov;
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}
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if (a.length < 3)
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throw new UnsupportedOperationException(k);
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a = (Object[])a[2];
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}
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}
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public Set<String> keySet() {
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return new AbstractSet<String> () {
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public int size() {
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return size;
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}
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public Iterator<String> iterator() {
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return new Iterator<String>() {
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private int i = -1;
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Object[] a = null;
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String cur = null;
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private boolean findNext() {
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if (a != null) {
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if (a.length == 3) {
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a = (Object[])a[2];
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cur = (String)a[0];
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return true;
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}
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i++;
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a = null;
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}
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cur = null;
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if (i >= rows)
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return false;
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if (i < 0 || ht[i] == null) {
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do {
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if (++i >= rows)
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return false;
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} while (ht[i] == null);
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}
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a = (Object[])ht[i];
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cur = (String)a[0];
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return true;
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}
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public boolean hasNext() {
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if (cur != null)
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return true;
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return findNext();
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}
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public String next() {
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if (cur == null) {
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if (!findNext())
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throw new NoSuchElementException();
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}
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String s = cur;
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cur = null;
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return s;
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}
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public void remove() {
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throw new UnsupportedOperationException();
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}
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};
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}
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};
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}
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public Set<Map.Entry<String,V>> entrySet() {
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return new AbstractSet<Map.Entry<String,V>> () {
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public int size() {
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return size;
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}
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public Iterator<Map.Entry<String,V>> iterator() {
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return new Iterator<Map.Entry<String,V>>() {
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final Iterator<String> i = keySet().iterator();
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public boolean hasNext() {
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return i.hasNext();
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}
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public Map.Entry<String,V> next() {
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return new Map.Entry<String,V>() {
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String k = i.next();
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public String getKey() { return k; }
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public V getValue() { return get(k); }
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public int hashCode() {
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V v = get(k);
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return (k.hashCode()
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+ (v == null
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? 0
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: v.hashCode()));
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}
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public boolean equals(Object ob) {
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if (ob == this)
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return true;
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if (!(ob instanceof Map.Entry))
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return false;
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Map.Entry<?,?> that = (Map.Entry<?,?>)ob;
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return ((this.getKey() == null
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? that.getKey() == null
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: this.getKey()
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.equals(that.getKey()))
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&&
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(this.getValue() == null
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? that.getValue() == null
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: this.getValue()
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.equals(that.getValue())));
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}
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public V setValue(V v) {
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throw new UnsupportedOperationException();
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}
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};
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}
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public void remove() {
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throw new UnsupportedOperationException();
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}
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};
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}
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};
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}
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}
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