Complete the two classes in java: (please show output)

1. ExpressionTree is a class to encapsulate information for an expression tree. Use the values 3.23 for a, 5.45 for b, -4.56 for c, 10.2 for d, -2.33 for e, 2.01 for f, 9.99 for g

2. DriverExpressionTree is a class to test the ExpressionTree class. It first creates an ExpressionTree to represent the expression tree shown below:

You must create an ExpressionTree for each subtree starting with the leaves and working your way up the tree to the root. It will begin like this:

ExpressionTree a = new ExpressionTree("a");

ExpressionTree b = new ExpressionTree("b");

ExpressionTree abPlus = new ExpressionTree();

abPlus.setTree("+", a, b);

and will end with

ExpressionTree myTree = new ExpressionTree();

myTree.setTree(three parameters);

Then the program will evaluate myTree and carry out the two traversals

---------------------DriverExpressionTree.java--------------------

/ This class will test the methods from ExpressionTree // Complete ExpressionTree class first and then // hardcode in the tree from the assignment

import TreePackage.ExpressionTree; import java.util.Iterator;

public class DriverExpressionTree { public static void main(String[] args) { // Build expression tree called myTree // for the tree shown in the assignment // Output evaluation and traversals System.out.println("Expression Tree evaluates to " + myTree.evaluate()); myTree.displayTree(); }

---------------------ExpressionTree.java--------------------

package TreePackage;

// This is a class to represent an expression tree // As noted below, some of the methods are incomplete // You should complete the unfinished methods // Do not change other methods or add any new ones

public class ExpressionTree extends BinaryTree implements ExpressionTreeInterface { public ExpressionTree() { }

public ExpressionTree(String rootData) { super(rootData); }

public double evaluate() { return evaluate(getRootNode()); } // complete the recursive method below // method will evaluate an expression tree rooted at rootNode private double evaluate(BinaryNode rootNode) { double result;

if (rootNode == null) result = 0; else if (rootNode.isLeaf()) { // result is the value of the rootNode

} else { // use recursion to calculate result based on the results // of the left subtree and the right subtree and the // operation in rootNode

}

return result; } private double getValueOf(String variable) { // Method returns the value of any possible variable

}

private double compute(String operator, double firstOperand, double secondOperand) { // Calculate the result of the operator on the two operands

}

// For testing purposes. Do not change public void displayTree() { BinaryNode rootNode = (BinaryNode)getRootNode(); System.out.println("preorder:"); preorder(rootNode); System.out.println(); System.out.println("postorder:"); rootNode = (BinaryNode)getRootNode(); postorder(rootNode); System.out.println(); }

// Carries out a postorder traversal on the tree rooted at rootNode // Method will print the node's data when it visits the node private void postorder(BinaryNode rootNode) { if (rootNode != null) {

} }

// Carries out a preorder traversal on the tree rooted at rootNode // Method will print the node's data when it visits the node private void preorder(BinaryNode rootNode) { if (rootNode != null) {

} } }