ExpressionTree

java.lang.Object
- TreeNode
- - ExpressionTree

All Implemented Interfaces:

Expressions
```
public class ExpressionTree
extends TreeNode
implements Expressions
```
The ExpressionTree class is a subclass of TreeNode and implements Expressions. The key methods are: buildTree, evalTree, toPrefixNotation, toInfixNotation, toPostfixNotation, and postfixEval. These methods enable this class to build binary trees to represent expressions, evaluate said trees, and convert them into prefix, infix and postfix notation. Finally, this class also has the postfixEval method, which evaluates the expression using a stack rather than recursively like evalTree, toPrefixNotation, toInfixNotation, and toPostfixNotation.

Author:

AnneMarie Caballero (annemariecabs)

See Also:

TreeNode

Field Summary

Fields
Modifier and Type	Field	Description
`private static java.lang.String`	`CLOSED_PAREN`	A closed parentheses
`private static java.lang.String`	`EMPTY`	An empty string
`private static java.lang.String`	`OPEN_PAREN`	An open parentheses
`private static java.lang.String`	`PLUS_SIGN`	A plus sign
`private static java.lang.String`	`SPACE`	A space
`private static java.lang.String`	`TIMES_SIGN`	A multiplication sign

Constructor Summary

Constructors
Constructor	Description
`ExpressionTree(java.lang.String initValue)`	Constructs a leaf, an ExpressionTree with a value but no left or right node, using the superclass's similar constructor method.
`ExpressionTree(java.lang.String initValue, TreeNode initLeft, TreeNode initRight)`	Constructs an ExpressionTree with a value, and using a left and right node, by using the superclass's constructor.
`ExpressionTree(TreeNode treeNode)`	Constructs an ExpressionTree by copying the values of the TreeNode passed to it

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`TreeNode`	`buildTree(java.lang.String[] exp)`	Builds a tree to represent the expression using a String[], where each item of the array is an element in a postfix expression.
`int`	`evalTree()`	Recursively evaluates the tree starting with the root.
`int`	`postfixEval(java.lang.String[] exp)`	Uses a stack to evaluate the expression given by exp, rather than building a tree and evaluating the tree.
`java.lang.String`	`toInfixNotation()`	Recursively converts the ExpressionTree to a String in infix notation (including parentheses around each individual expression within the wider expression).
`java.lang.String`	`toPostfixNotation()`	Recursively converts the ExpressionTree to a String in postfix notation.
`java.lang.String`	`toPrefixNotation()`	Recursively converts the ExpressionTree to a String in prefix notation.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from class TreeNode
getLeft, getRight, getValue, setLeft, setRight, setValue

- Field Detail
  - PLUS_SIGN
```
private static final java.lang.String PLUS_SIGN
```
    A plus sign
    
    See Also:
    
    Constant Field Values
  - TIMES_SIGN
```
private static final java.lang.String TIMES_SIGN
```
    A multiplication sign
    
    See Also:
    
    Constant Field Values
  - EMPTY
```
private static final java.lang.String EMPTY
```
    An empty string
    
    See Also:
    
    Constant Field Values
  - SPACE
```
private static final java.lang.String SPACE
```
    A space
    
    See Also:
    
    Constant Field Values
  - OPEN_PAREN
```
private static final java.lang.String OPEN_PAREN
```
    An open parentheses
    
    See Also:
    
    Constant Field Values
  - CLOSED_PAREN
```
private static final java.lang.String CLOSED_PAREN
```
    A closed parentheses
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - ExpressionTree
```
public ExpressionTree(java.lang.String initValue)
```
    Constructs a leaf, an ExpressionTree with a value but no left or right node, using the superclass's similar constructor method.
    
    Parameters:
    
    initValue - the value of the ExpressionTree created
  - ExpressionTree
```
public ExpressionTree(java.lang.String initValue,
                      TreeNode initLeft,
                      TreeNode initRight)
```
    Constructs an ExpressionTree with a value, and using a left and right node, by using the superclass's constructor.
    
    Parameters:
    
    initValue - the value of this ExpressionTree
    
    initLeft - the left node of this ExpressionTree
    
    initRight - the right node of this ExpressionTree
  - ExpressionTree
```
public ExpressionTree(TreeNode treeNode)
```
    Constructs an ExpressionTree by copying the values of the TreeNode passed to it
    
    Parameters:
    
    treeNode - the TreeNode to be copied
- Method Detail
  - buildTree
```
public TreeNode buildTree(java.lang.String[] exp)
```
    Builds a tree to represent the expression using a String[], where each item of the array is an element in a postfix expression.
    
    Specified by:
    
    buildTree in interface Expressions
    
    Parameters:
    
    exp - a String[] holding the elements of an expression
    
    Returns:
    
    a TreeNode representing the root of the expression
  - evalTree
```
public int evalTree()
```
    Recursively evaluates the tree starting with the root.
    
    Specified by:
    
    evalTree in interface Expressions
    
    Returns:
    
    an integer result of the expression represented by the tree
  - toPrefixNotation
```
public java.lang.String toPrefixNotation()
```
    Recursively converts the ExpressionTree to a String in prefix notation.
    
    Specified by:
    
    toPrefixNotation in interface Expressions
    
    Returns:
    
    a String representing the expression in prefix notation
  - toInfixNotation
```
public java.lang.String toInfixNotation()
```
    Recursively converts the ExpressionTree to a String in infix notation (including parentheses around each individual expression within the wider expression).
    
    Specified by:
    
    toInfixNotation in interface Expressions
    
    Returns:
    
    a String representing the expression in infix notation
  - toPostfixNotation
```
public java.lang.String toPostfixNotation()
```
    Recursively converts the ExpressionTree to a String in postfix notation.
    
    Specified by:
    
    toPostfixNotation in interface Expressions
    
    Returns:
    
    a String representing the expression in postfix notation
  - postfixEval
```
public int postfixEval(java.lang.String[] exp)
```
    Uses a stack to evaluate the expression given by exp, rather than building a tree and evaluating the tree.
    
    Specified by:
    
    postfixEval in interface Expressions
    
    Parameters:
    
    exp - the expression to be evaluated where each item of the String[] represents an item in the expression
    
    Returns:
    
    the result of the expression

Class ExpressionTree

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from class TreeNode

Field Detail

PLUS_SIGN

TIMES_SIGN

EMPTY

SPACE

OPEN_PAREN

CLOSED_PAREN

Constructor Detail

ExpressionTree

ExpressionTree

ExpressionTree

Method Detail

buildTree

evalTree

toPrefixNotation

toInfixNotation

toPostfixNotation

postfixEval