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package org.netbeans.modules.ruby.spi.project.support.rake;
import java.beans.PropertyChangeListener;
import java.util.Map;
/**
* A way of mapping property names to values.
* <p>
* This interface defines no independent thread safety, but in typical usage
* it will be used with the project manager mutex. Changes should be fired
* synchronously.
* @author Jesse Glick
* @see PropertyUtils#sequentialPropertyEvaluator
* @see RakeProjectHelper#getStandardPropertyEvaluator
*/
public interface PropertyEvaluator {
/**
* Evaluate a single property.
* @param prop the name of a property
* @return its value, or null if it is not defined or its value could not be
* retrieved for some reason (e.g. a circular definition)
*/
String getProperty(String prop);
/**
* Evaluate a block of text possibly containing property references.
* The syntax is the same as for Ant: <samp>${foo}</samp> means the value
* of the property <samp>foo</samp>; <samp>$$</samp> is an escape for
* <samp>$</samp>; references to undefined properties are left unsubstituted.
* @param text some text possibly containing one or more property references
* @return its value, or null if some problem (such a circular definition) made
* it impossible to retrieve the values of some properties
*/
String evaluate(String text);
/**
* Get a set of all current property definitions at once.
* This may be more efficient than evaluating individual properties,
* depending on the implementation.
* @return an immutable map from property names to values, or null if the
* mapping could not be computed (e.g. due to a circular definition)
*/
Map<String,String> getProperties();
/**
* Add a listener to changes in particular property values.
* As generally true with property change listeners, the old and new
* values may both be null in case the true values are not known or not
* easily computed; and the property name might be null to signal that any
* property might have changed.
* @param listener a listener to add
*/
void addPropertyChangeListener(PropertyChangeListener listener);
/**
* Remove a listener to changes in particular property values.
* @param listener a listener to remove
*/
void removePropertyChangeListener(PropertyChangeListener listener);
}
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