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Jadex Rules is a small lightweight rule engine, which currently employs the well-known Rete algorithm for highly efficient rule matching. Jadex rules is therefore similar to other rule engines like JESS and Drools. Despite the similarities there are also important differences between these systems: * Jadex Rules is very small and intended to be used as component of other software. Even though rules can be specified in a Java dialect as well as (a small variation of) the CLIPS language its primary usage is on the API level. Jadex Rules is currently the core component of the Jadex BDI reasoning engine. * Jadex Rules cleanly separates between state and rule representation. This allows the state implementation as well as the matcher to be flexibly exchanged. Some experiments have e.g. been conducted with a Jena representation. Regarding the matcher, it is planned to support also the Treat algorithm, which has a lower memory footprint than Rete. * Jadex Rules pays close attention to rule debugging. The state as well as the rete engine can be observed at runtime. The rule debugger provides functionalities to execute a rule program stepwise and also use rule breakpoints to stop the execution at those points.

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package jadex.rules.parser.conditions.javagrammar;

import jadex.commons.SUtil;
import jadex.rules.rulesystem.rules.Variable;


/**
 *  A literal is a constant value.
 */
public class LiteralExpression	extends Expression
{
	//-------- attributes --------
	
	/** The literal value. */
	protected Object	value;
	
	//-------- constructors --------
	
	/**
	 *  Create a new literal.
	 */
	public LiteralExpression(Object value)
	{
		this.value	= value;
	}
	
	//-------- methods --------
	
	/**
	 *  Test if a variable is contained in the expression.
	 *  @param var	The variable.
	 *  @return	True, when the variable is contained.
	 */
	public boolean	containsVariable(Variable var)
	{
		return false;
	}
	
	/**
	 *  Get the value.
	 */
	public Object	getValue()
	{
		return this.value;
	}
	
	/**
	 *  Get a string representation of this value.
	 */
	public String	toString()
	{
		return value!=null ? value.toString() : "null";
	}

	/**
	 *  Test if this value is equal to some object.
	 */
	public boolean	equals(Object o)
	{
		return o instanceof LiteralExpression
			&& SUtil.equals(((LiteralExpression)o).getValue(), getValue());
	}
	
	/**
	 *  Get the hash code of this variable.
	 */
	public int	hashCode()
	{
		return 31 + (getValue()!=null ? getValue().hashCode() : 0);
	}
}