package org.jbpm.pvm.internal.script;
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import javax.script.ScriptContext;
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import java.util.*;
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import static javax.script.ScriptContext.*;
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/**
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* This class implements an ENGINE_SCOPE centric Map view of the ScriptContext
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* for engine implementations. This class can be used to simplify engine
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* implementations which have the capability to bind their namespaces to Maps
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* or other external interfaces.
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*
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* Get operations on this view delegate to the
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* ScriptContext inheriting get() method that automatically traverses the
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* binding scopes in order or precedence. Put operations on this view always
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* store values in the ENGINE_SCOPE bindings. Other operations such as
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* size() and contains() are implemented appropriately, but perhaps not as
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* efficiently as possible.
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*
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*/
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public class ScriptContextEngineView implements Map<String,Object>
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{
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ScriptContext context;
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public ScriptContextEngineView( ScriptContext context )
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{
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this.context = context;
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}
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/**
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* Returns the number of unique object bindings in all scopes.
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* (duplicate, shadowed, bindings count as a single binging).
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*/
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public int size()
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{
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return totalKeySet().size();
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}
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/**
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* Returns true if no bindings are present in any scope of the context.
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*/
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public boolean isEmpty()
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{
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return totalKeySet().size() == 0;
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}
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/**
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* Returns true if the key name is bound in any scope in the context.
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* The key must be a String.
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*
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* @param key key whose presence in this map is to be tested.
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*
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* @return <tt>true</tt> if this map contains a mapping for the specified key.
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*
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* @throws ClassCastException if the key is of an inappropriate type for this
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* map (optional).
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* @throws NullPointerException if the key is <tt>null</tt> and this map does
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* not permit <tt>null</tt> keys (optional).
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*/
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// Why isn't the compiler allowing this?
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//public boolean containsKey( String key )
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public boolean containsKey( Object key )
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{
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return context.getAttribute( (String)key ) != null;
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}
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/**
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* Returns <tt>true</tt> if this map maps one or more keys to the specified
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* value. More formally, returns <tt>true</tt> if and only if this map
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* contains at least one mapping to a value <tt>v</tt> such that
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* <tt>(value==null ? v==null : value.equals(v))</tt>. This operation will
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* probably require time linear in the map size for most implementations of the
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* <tt>Map</tt> interface.
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*
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* @param value value whose presence in this map is to be tested.
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*
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* @return <tt>true</tt> if this map maps one or more keys to the specified
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* value.
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*
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* @throws ClassCastException if the value is of an inappropriate type for this
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* map (optional).
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* @throws NullPointerException if the value is <tt>null</tt> and this map does
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* not permit <tt>null</tt> values (optional).
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*/
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public boolean containsValue( Object value )
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{
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Set values = totalValueSet();
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return values.contains( value );
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}
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/**
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* Returns the value bound in the most specific (lowest numbered)
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* bindings space for this key.
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* key must be a String.
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*
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* @param key key whose associated value is to be returned.
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*
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* @return the value to which this map maps the specified key, or <tt>null</tt>
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* if the map contains no mapping for this key.
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*
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* @throws ClassCastException if the key is of an inappropriate type for this
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* map (optional).
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* @throws NullPointerException if the key is <tt>null</tt> and this map does
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* not permit <tt>null</tt> keys (optional).
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* @see #containsKey(Object)
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*/
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public Object get( Object key )
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{
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return context.getAttribute( (String)key );
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}
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/**
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* Set the key, value binding in the ENGINE_SCOPE of the context.
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*
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* @param key key with which the specified value is to be associated.
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* @param value value to be associated with the specified key.
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*
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* @return previous value associated with specified key, or <tt>null</tt> if
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* there was no mapping for key. A <tt>null</tt> return can also
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* indicate that the map previously associated <tt>null</tt> with the
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* specified key, if the implementation supports <tt>null</tt> values.
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*
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* @throws UnsupportedOperationException if the <tt>put</tt> operation is not
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* supported by this map.
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* @throws ClassCastException if the class of the specified key or value
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* prevents it from being stored in this map.
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* @throws IllegalArgumentException if some aspect of this key or value
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* prevents it from being stored in this map.
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* @throws NullPointerException if this map does not permit <tt>null</tt> keys
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* or values, and the specified key or value is <tt>null</tt>.
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*/
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public Object put( String key, Object value )
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{
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Object oldValue =
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context.getAttribute( key, ENGINE_SCOPE );
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context.setAttribute( key, value, ENGINE_SCOPE );
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return oldValue;
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}
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/**
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* Put the bindings into the ENGINE_SCOPE of the context.
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*
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* @param t Mappings to be stored in this map.
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*
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* @throws UnsupportedOperationException if the <tt>putAll</tt> method is not
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* supported by this map.
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* @throws ClassCastException if the class of a key or value in the specified
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* map prevents it from being stored in this map.
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* @throws IllegalArgumentException some aspect of a key or value in the
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* specified map prevents it from being stored in this map.
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* @throws NullPointerException if the specified map is <tt>null</tt>, or if
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* this map does not permit <tt>null</tt> keys or values, and the specified map
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* contains <tt>null</tt> keys or values.
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*/
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public void putAll( Map<? extends String, ? extends Object> t )
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{
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context.getBindings( ENGINE_SCOPE ).putAll( t );
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}
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/**
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* Removes the mapping from the engine scope.
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* <p/>
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* <p>Returns the value to which the map previously associated the key, or
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* <tt>null</tt> if the map contained no mapping for this key. (A
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* <tt>null</tt> return can also indicate that the map previously associated
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* <tt>null</tt> with the specified key if the implementation supports
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* <tt>null</tt> values.) The map will not contain a mapping for the specified
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* key once the call returns.
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*
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* @param okey key whose mapping is to be removed from the map.
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*
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* @return previous value associated with specified key, or <tt>null</tt> if
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* there was no mapping for key.
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*
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* @throws ClassCastException if the key is of an inappropriate type for this
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* map (optional).
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* @throws NullPointerException if the key is <tt>null</tt> and this map does
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* not permit <tt>null</tt> keys (optional).
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* @throws UnsupportedOperationException if the <tt>remove</tt> method is not
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* supported by this map.
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*/
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// Why is the compiler complaining about this?
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//public Object remove( String key )
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public Object remove( Object okey )
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{
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// This shouldn't be necessary... we don't map Objects, Strings.
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String key = (String)okey;
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Object oldValue =
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context.getAttribute( key, ENGINE_SCOPE );
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context.removeAttribute( key, ENGINE_SCOPE );
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return oldValue;
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}
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/**
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* Removes all mappings from this map (optional operation).
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*
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* @throws UnsupportedOperationException clear is not supported by this map.
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*/
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public void clear()
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{
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context.getBindings( ENGINE_SCOPE ).clear();
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}
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/**
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* Returns the total key set of all scopes.
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* This method violates the Map contract by returning an unmodifiable set.
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*
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* @return a set view of the keys contained in this map.
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*/
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public Set keySet()
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{
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return totalKeySet();
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}
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/**
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*
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* Returns the total values set of all scopes.
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* This method violates the Map contract by returning an unmodifiable set.
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*
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* @return a collection view of the values contained in this map.
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*/
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public Collection values()
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{
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return totalValueSet();
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}
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/**
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* Returns a set view of the mappings contained in this map. Each element in
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* the returned set is a {@link java.util.Map.Entry}. The set is backed by the
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* map, so changes to the map are reflected in the set, and vice-versa. If the
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* map is modified while an iteration over the set is in progress (except
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* through the iterator's own <tt>remove</tt> operation, or through the
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* <tt>setValue</tt> operation on a map entry returned by the iterator) the
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* results of the iteration are undefined. The set supports element removal,
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* which removes the corresponding mapping from the map, via the
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* <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>,
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* <tt>retainAll</tt> and <tt>clear</tt> operations. It does not support the
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* <tt>add</tt> or <tt>addAll</tt> operations.
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*
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* @return a set view of the mappings contained in this map.
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*/
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public Set<Entry<String,Object>> entrySet()
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{
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throw new Error("unimplemented");
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}
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private Set totalKeySet()
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{
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Set keys = new HashSet();
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List<Integer> scopes = context.getScopes();
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for ( int i : scopes ) {
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keys.addAll( context.getBindings( i ).keySet() );
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}
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return Collections.unmodifiableSet(keys);
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}
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private Set totalValueSet()
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{
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Set values = new HashSet();
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List<Integer> scopes = context.getScopes();
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for ( int i : scopes ) {
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values.addAll( context.getBindings( i ).values() );
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}
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return Collections.unmodifiableSet(values);
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}
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}
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