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package com.sun.jersey.client.impl;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * A basic copy on write HashMap.
 * 

* If an instance is cloned then any methods invoked on the instance or clone * that result in state modification will result in copying of the state * before modification. * * @author [email protected] * @author [email protected] */ public class CopyOnWriteHashMap implements Map { private volatile Map core; private volatile Map view; private final AtomicBoolean requiresCopyOnWrite; public CopyOnWriteHashMap() { this.core = new HashMap(); this.requiresCopyOnWrite = new AtomicBoolean(false); } private CopyOnWriteHashMap(CopyOnWriteHashMap that) { this.core = that.core; this.requiresCopyOnWrite = new AtomicBoolean(true); } @Override public CopyOnWriteHashMap clone() { try { return new CopyOnWriteHashMap(this); } finally { requiresCopyOnWrite.set(true); } } private void copy() { if (requiresCopyOnWrite.compareAndSet(true, false)) { core = new HashMap(core); view = null; } } @Override public int size() { return core.size(); } @Override public boolean isEmpty() { return core.isEmpty(); } @Override public boolean containsKey(Object key) { return core.containsKey(key); } @Override public boolean containsValue(Object value) { return core.containsValue(value); } @Override public V get(Object key) { return core.get(key); } @Override public V put(K key, V value) { copy(); return core.put(key,value); } @Override public V remove(Object key) { copy(); return core.remove(key); } @Override public void putAll(Map t) { copy(); core.putAll(t); } @Override public void clear() { core = new HashMap(); copy(); } @Override public Set keySet() { return getView().keySet(); } @Override public Collection values() { return getView().values(); } @Override public Set> entrySet() { return getView().entrySet(); } @Override public String toString() { return core.toString(); } private Map getView() { if (view == null) { view = Collections.unmodifiableMap(core); } return view; } }





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