fido.util
Class BooleanTree

java.lang.Object
  |
  +--fido.util.BooleanTree

All Implemented Interfaces:

java.io.Serializable

public class BooleanTree

extends java.lang.Object

implements java.io.Serializable

This class represents a boolean expression. Example expression: (A = B) & ((C != D) | (E = F)). The BooleanTree contains two types of nodes: BooleanNode and any BooleanTreeNode as a leaf node. The a subclass of BooleanNode, either BooleanAndNode or BooleanOrNode, will join two subtrees by specifying both must be successful (AND), or either one may be successful (OR).

A sample usage would be:

• Create a new empty tree with the constructor BooleanTree()
• Create a leaf node
• Add a value node class to the tree with bt.addLeafNode()
• Add a boolean node to the tree with bt.addBooleanAndNode()
• Create a leaf node
• Add a final value node class to the tree with bt.addLeafNode()

After loading the tree, call getRootNode() which will validate the tree is correct, and return a BooleanTreeNode, which can be used to traverse the tree.

Parenthesis are handled by two calls startGroup() and endGroup().

See Also:

Serialized Form

Constructor Summary

BooleanTree()
Construct an empty BooleanTree.

Method Summary

void	addBooleanAndNode() Creates a BooleanAndNode to be inserted into the tree.
void	addBooleanOrNode() Creates a BooleanOrNode to be inserted into the tree.
void	addLeafNode(BooleanTreeNode node) Add a leaf node to the tree.
void	endGroup() Closes a currently open parenthesis group.
BooleanTreeNode	getRootNode() After filling the BooleanTree, this call will validate the tree is correct using the validateTree() call, then return the root node of the tree for traversal.
void	startGroup() Starts a new parenthesis group.
void	validateTree() Used to validate the tree is properly formed: All parenthesis are closed The last boolean node contains a right branch.

Methods inherited from class java.lang.Object

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

Constructor Detail

BooleanTree

public BooleanTree()

Construct an empty BooleanTree.

Method Detail

getRootNode

public BooleanTreeNode getRootNode()
                            throws BooleanSyntaxException

After filling the BooleanTree, this call will validate the tree is correct using the validateTree() call, then return the root node of the tree for traversal.

BooleanSyntaxException

See Also:

validateTree()

addLeafNode

public void addLeafNode(BooleanTreeNode node)
                 throws BooleanSyntaxException

Add a leaf node to the tree.

Parameters:

node - any Object that implements BooleanTreeNode

Throws:

BooleanSyntaxException - Thrown when adding a leaf node immediately after adding a previous leaf node. A leaf node must be the first node, or added after a BooleanNode.

See Also:

BooleanTreeNode

addBooleanAndNode

public void addBooleanAndNode()
                       throws BooleanSyntaxException

Creates a BooleanAndNode to be inserted into the tree. This means that both the left and right branches must evaluate to true.

Throws:

BooleanSyntaxException - Thrown when no nodes are present in the tree. A subclas of BooleanNode cannot be the first node in the tree. For example, the following expression is invalid: & (A = C)

See Also:

BooleanAndNode

addBooleanOrNode

public void addBooleanOrNode()
                      throws BooleanSyntaxException

Creates a BooleanOrNode to be inserted into the tree. This means that both the left or right branches must evaluate to true.

Throws:

BooleanSyntaxException - Thrown when no nodes are present in the tree. A subclas of BooleanNode cannot be the first node in the tree. For example, the following expression is invalid: & (A = C)

See Also:

BooleanOrNode

startGroup

public void startGroup()

Starts a new parenthesis group.

endGroup

public void endGroup()
              throws BooleanSyntaxException

Closes a currently open parenthesis group.

Throws:

BooleanSyntaxException - Thrown if no parenthese groups are open or if a boolean node is the last node in the group.

validateTree

public void validateTree()
                  throws BooleanSyntaxException

Used to validate the tree is properly formed:

• All parenthesis are closed
• The last boolean node contains a right branch.

If any error is found, a BooleanSyntaxException is thrown.

Throws:

BooleanSyntaxException - Thrown if an error in the tree is found. See list above.