Class BooleanExpression

Object

BooleanExpression

public class BooleanExpression
extends Object

Constructor Summary

Constructors

Constructor and Description
BooleanExpression(String s) Given a boolean expression as a string, parses it into a BooleanExpression object that can manipulate and evaluate it.

Method Summary

Methods

Modifier and Type	Method and Description
Boolean	evaluate(Map<String,Boolean> assignments) Returns true if the given assignments force this boolean expression to be true, false if they force it to be false, and null if it could be either true or false.
Set<String>	getVariables() Returns a set of the variables in this boolean expression.
boolean	isAnd() Returns true if the top level of this boolean expression is an and and false otherwise.
boolean	isNot() Returns true if the top level of this boolean expression is a not and false otherwise.
boolean	isOr() Returns true if the top level of this boolean expression is an or and false otherwise.
boolean	isVariable() Returns true if this boolean expression is a variable and false otherwise.
String	toString() Returns a string representation of this boolean expression.

Methods inherited from class Object

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

Constructor Detail

BooleanExpression

public BooleanExpression(String s)

Given a boolean expression as a string, parses it into a BooleanExpression object that can manipulate and evaluate it. For example, the following are valid inputs:

• "(a || !b)"
• "!((a && (!b && c)) || d)

Parameters:

s - A string representation of the expression to create.

Method Detail

isVariable

public boolean isVariable()

Returns true if this boolean expression is a variable and false otherwise. For example:

• "a" is a variable
• "!a" is NOT a variable
• "a && b" is NOT a variable

isOr

public boolean isOr()

Returns true if the top level of this boolean expression is an or and false otherwise. For example:

• "a || b" is an or
• "a || (b && c)" is an or
• "a && (b || c)" is NOT an or
• "a" is NOT an or
• "!(a || b)" is NOT an or

isAnd

public boolean isAnd()

Returns true if the top level of this boolean expression is an and and false otherwise. For example:

• "a && b" is an and
• "a && (b || c)" is an and
• "a || (b && c)" is NOT an and
• "a" is NOT an and
• "!(a && b)" is NOT an and

isNot

public boolean isNot()

Returns true if the top level of this boolean expression is a not and false otherwise. For example:

• "!(a && b)" is a not
• "!(a && (b || c))" is a not
• "!a || !(b && c)" is NOT a not
• "a" is NOT a not
• "a && b" is NOT a not

toString

public String toString()

Returns a string representation of this boolean expression.

Overrides:

toString in class Object

getVariables

public Set<String> getVariables()

Returns a set of the variables in this boolean expression. For example:

• If the boolean expression were "a || b", then this method would return ["a", "b"].
• If the boolean expression were "(!a || (!b || (a && c)))", this method would return ["a", "b", "c"].

evaluate

public Boolean evaluate(Map<String,Boolean> assignments)

Returns true if the given assignments force this boolean expression to be true, false if they force it to be false, and null if it could be either true or false. For example:

• If the boolean expression is "(a || b) && c", and the assignments are: {"a"=true}, then "true || b) && c" is not necessarily true AND it's not necessarily false. So, this method would return null.
• If the boolean expression is "(a || b) && c", and the assignments were {"a"=true, "c"=true}, then we would have "(true || b) && true" which is always true; so, this method would return true.

Parameters:

assignments - A (partial) map from variables to truth values.