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org.josql.expressions
Class AndOrExpression  

java.lang.Object
  org.josql.expressions.Expression
      org.josql.expressions.BinaryExpression
          org.josql.expressions.AndOrExpression

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public class AndOrExpression

extends BinaryExpression

Represents either an AND expression or a OR expression. Lazy evaluation is employed here such if the expression is: LHS OR RHS and LHS = true then the RHS is NOT evaluated, if the expression is: LHS AND RHS and LHS = false then the RHS is NOT evaluated (see isTrue(Object,Query) 55 ). This is important to note if you expect side-effects to occur in the RHS (bad practice anyway so don't do it!).

Last Modified By: $Author: barrygently $
Last Modified On: $Date: 2004/12/20 16:22:43 $
Current Revision: $Revision: 1.2 $

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Field Summary
private  boolean	and

 

Fields inherited from class org.josql.expressions.BinaryExpression

left, right

 

Fields inherited from class org.josql.expressions.Expression

 

Constructor Summary

AndOrExpression()

 

Method Summary
boolean	isAnd()
boolean	isTrue(java.lang.Object o, org.josql.Query q)           Evaulates the expression and returns true if the expression evaulates to true.
void	setAnd(boolean v)
java.lang.String	toString()           Return a string version of this expression.

 

Methods inherited from class org.josql.expressions.BinaryExpression

getExpectedReturnType, getLeft, getRight, getValue, hasFixedResult, init, setLeft, setRight

 

Methods inherited from class org.josql.expressions.Expression

isBracketed, setBracketed

 

Methods inherited from class java.lang.Object

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

 

Field Detail

and

private boolean and

Constructor Detail

AndOrExpression

public AndOrExpression()

Method Detail

isAnd

public boolean isAnd()

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setAnd

public void setAnd(boolean v)

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isTrue

public boolean isTrue(java.lang.Object o,
                      org.josql.Query q)
               throws org.josql.QueryExecutionException

Evaulates the expression and returns true if the expression evaulates to true.

Type	LHS	RHS	Result	Notes
AND	true	true	true	Both LHS and RHS are evaulated.
AND	true	false	false	Both LHS and RHS are evaulated.
AND	false	unknown or false	false	Only the LHS is evaulated.
OR	true	unknown	true	Only the LHS is evaulated.
OR	false	true	true	Both the LHS and RHS are evaulated.
OR	false	false	false	Both the LHS and RHS are evaulated.

In general what this means is that you should "left-weight" your expressions so that the expression that returns true most often (or more likely to return true) should be on the LHS.

Specified by:

isTrue in class Expression

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toString

public java.lang.String toString()

Return a string version of this expression. Note: any formatting of the statement (such as line breaks) will be removed.

Specified by:

toString in class Expression

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