net.christopherschultz.evaluator
Class Expression

java.lang.Object
  net.christopherschultz.evaluator.Expression

Direct Known Subclasses:

ArrayReferenceExpression, BinaryOperatorExpression, ConstantExpression, FunctionCallExpression, NegatedExpression, UnaryMinusExpression

public abstract class Expression
extends Object

An evaluatable Expression. To obtain an Expression, you should use the ExpressionParser class:

 Expression exp = ExpressionParser.parseExpression("1 + 2 + 3 * 5");
 

This expression can later be evaluated:

 EvaluationContext ctx = ...;
 Object result = exp.evaluate(ctx);
 

The expression in the example will return an Integer result.

Version:

$Revision: 1.3 $ $Date: 2008-06-20 22:58:48 $

Author:

Chris Schultz

Constructor Summary

Expression()

Method Summary

abstract void	acceptVisitor(ExpressionVisitor visitor) Accepts an ExpressionVisitor.
abstract Object	evaluate(EvaluationContext ec) Evaluates this expression and returns the result.
Expression	getParent()
abstract List	getSubExpressions() Gets a flattened, depth-first traversal of the expressions in this Expression (including this Expression).
protected void	setParent(Expression parent)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Expression

public Expression()

Method Detail

evaluate

public abstract Object evaluate(EvaluationContext ec)
                         throws EvaluationException

Evaluates this expression and returns the result. This method is not threadsafe, but is idempotent (repeatable with the same result).

Parameters:

ec - The context in which this expression should be evaluated.

Returns:

The result of evaluating this Expression. This may by an object of any type, including null.

Throws:

EvaluationException - If there is an error evaluating this Expression.

getSubExpressions

public abstract List getSubExpressions()

Gets a flattened, depth-first traversal of the expressions in this Expression (including this Expression).

Returns:

A List of sub-expressions for this Expression.

acceptVisitor

public abstract void acceptVisitor(ExpressionVisitor visitor)

Accepts an ExpressionVisitor.

setParent

protected void setParent(Expression parent)
                  throws EvaluationException

Throws:

EvaluationException

getParent

public Expression getParent()