biz.chitec.quarterback.util.logic
Class AlgebraicExpr

java.lang.Object
  biz.chitec.quarterback.util.logic.AlgebraicExpr

All Implemented Interfaces:

java.lang.Cloneable, LogicExpr

Direct Known Subclasses:

ANDExpr, ORExpr

public abstract class AlgebraicExpr

extends java.lang.Object

implements LogicExpr

Common superclass for AND, OR and further operations of Boolean algebra

Version:

$Id: 0acf1a58945b4cb0f4e16063a4cbad812fe162c7 $

Author:

cantamen/Dirk Hillbrecht 2005. Distributed under the terms of the GNU LGPL.

Nested Class Summary

Nested classes inherited from class biz.chitec.quarterback.util.logic.LogicExpr

LogicExpr.Converter, LogicExpr.UniverseGenerator

Field Summary

protected java.util.List

expressions

Constructor Summary

protected	AlgebraicExpr()
protected	AlgebraicExpr(LogicExpr e1x, LogicExpr e2x)
protected	AlgebraicExpr(java.lang.Object[] os)

Method Summary

java.lang.Object	clone() Deep-copy the logic expression.
void	convertValues(LogicExpr.Converter c) Conversion of values in the expressions (e.g. for replacing external representations of database entries with their internal key)
boolean	equals(java.lang.Object o)
java.util.List	getExpressions() Return all expressions.
java.lang.Object[]	getInternalVars() Only for GJSA class parsers: get class variables to create object from a parsed string.
boolean	hasLeafsOnly() Returns whether the algebraic expression has only leaf nodes.
boolean	isReady() Returns if the expression is actually evaluable, i.e. any of the evaluating methods can be called.
boolean	isTreeReady() Returns whether this and all deeper expressions are evaluable.

Methods inherited from class java.lang.Object

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

Methods inherited from interface biz.chitec.quarterback.util.logic.LogicExpr

evaluate, getResultSet, sqlString

Field Detail

expressions

protected java.util.List expressions

Constructor Detail

AlgebraicExpr

protected AlgebraicExpr()

AlgebraicExpr

protected AlgebraicExpr(LogicExpr e1x,
                        LogicExpr e2x)

AlgebraicExpr

protected AlgebraicExpr(java.lang.Object[] os)

Method Detail

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Description copied from interface: LogicExpr

Deep-copy the logic expression. The contract for this method says the the logic expression must be deep-copied. I.e. if clone() is called for the root expression of a certain expression tree, a completely independent tree is returned.

Note: This method must be defined in a way that makes it quite complicated to call it for simply cloning a logic expression tree: It returns an Object (which always happens to be a LogicExpr) and it might throw a CloneNotSupportedException - which will (a) never happen and is (b) no RuntimeException, so a caller would always have to catch it.

To make life simpler, there is a static method LogicExprUtilties.cloneLogicExpr() which will call clone() on the root object and take care of return value and exceptions.

Specified by:

clone in interface LogicExpr

Throws:

java.lang.CloneNotSupportedException

equals

public boolean equals(java.lang.Object o)

hasLeafsOnly

public boolean hasLeafsOnly()

Returns whether the algebraic expression has only leaf nodes. This method allows to detect whether this algebraic expression has any further algebraic expressions below it. If this returns true, all children of this node are final children, i.e. no further algebraic operations come below this one.

Returns:

true if only leafs are below this expression, false otherwise.

isReady

public boolean isReady()

Description copied from interface: LogicExpr

Returns if the expression is actually evaluable, i.e. any of the evaluating methods can be called. If this method returns false, the expression should not be evaluated. Note that this method does not care for the evaluation state of any potential children of this LogicExpr. Use isTreeEvaluable() for this test.

Specified by:

isReady in interface LogicExpr

Returns:

True if an evaluation is possible, false if not.

isTreeReady

public boolean isTreeReady()

Description copied from interface: LogicExpr

Returns whether this and all deeper expressions are evaluable. Walks through the the expression tree and returns only true if all expressions below are evaluable.

Specified by:

isTreeReady in interface LogicExpr

Returns:

True if this and all expressions below are evaluable, false otherwise.

getExpressions

public java.util.List getExpressions()

Return all expressions. This method returns the real thing. It is possible to add or remove elements to and from the list which is reflected by the algebraic expression immediately

Returns:

Internal list of expressions

getInternalVars

public java.lang.Object[] getInternalVars()

Description copied from interface: LogicExpr

Only for GJSA class parsers: get class variables to create object from a parsed string.

Specified by:

getInternalVars in interface LogicExpr

convertValues

public void convertValues(LogicExpr.Converter c)

Description copied from interface: LogicExpr

Conversion of values in the expressions (e.g. for replacing external representations of database entries with their internal key)

Specified by:

convertValues in interface LogicExpr