Question

ECLIPSE

Extend the Arithrmetic example from the course notes to include classes Minus, Mult and Divide. Each of these should override the sxall) method to perform the correct operations. For each dass, induding the ones I've already provided, write a toString() method that returns a String containing a text version of the part of the arithmetic problem in the subtree rooted at the current node. For example, If the expression tree is calling toString() for the "node should produce the String The recommended way to do this is the same as the way the eval() method works recursively. For example, if the top node is a Plus object, it creates a String with an opening parenthesis "C", then calls its left child to return a String (which is then concatenated), then concatenates· ", then calls its right child to return a string (which is concatenated), then concatenates ". The method toString) returns the resultant String. Rewrite the TestArithmetic class so that its main () method produces five random arithmetic problems of length four (i.e., having four Consts separated by three operators). Constants should be integers chosen at random in the range [1, 20). Operators should be chosen randomly from the set(+,--. For each arithmetic problem, you should print out the result of your toStringO method applied to the root node, then an equals sign, then the result of exal(), producing something like this: ((16.0/16.0)-(7.0 17.0) 118.0 ((4.0 17.0)/(12.0/12.0))-21.0 ((14.0-4.0)+ (10/20.0))-10.05 ((18.0+ 15.0)/(5.0/10.0) 66.0 ((4.0/5.0)+ (5.0 7.0) 35.8 You might find it convenient (as I did) to create methods adQpsxatox) and

Answer 1

TestArithmetic.java

import java.util.Random;

public class TestArithmetic {
  
   static Random random = new Random();
  
   public static void main(String[] args) {
      
       for (int i = 0; i < 5; i++) {
           Node n = randOperator( randOperator( randConstant(), randConstant() ), randOperator( randConstant(), randConstant() ) );
           printResult(n);
       }
      
      
//       Node node2 = new Divide(randConstant(), new Const(0));
//       System.out.println(node2.eval());
   }
  
  
   public static Binop randOperator(Node l, Node r) {
       int operator = random.nextInt(4);
       switch (operator) {
       case 0:
           return new Plus(l, r);
       case 1:
           return new Minus(l, r);
       case 2:
           return new Mult(l, r);
       case 3:
           return new Divide(l, r);
       default:
           return null;
       }
   }
  
   public static Node randConstant() {
       int constant = random.nextInt(20) + 1; // generate constant integers randomly in the range from 1 to 20
       return new Const(constant);
   }
  
   public static void printResult(Node node) {
      
      
       double result = node.eval();
       int round = (int) (result * 10);
      
       if (result * 10 - (double) round != 0) {
           System.out.print(node.toString() + " = " );
           System.out.printf( "%.2f", node.eval() );
           System.out.println();
       } else {
           System.out.print(node.toString() + " = " );
           System.out.printf( "%.1f", node.eval() );
           System.out.println();      
       }
      
   }
  
}

Node.java

public class Node {
  
   /**
   * Constructor
   */
   public Node() {
   }
  
   /**
   * @return the evaluated value of this node
   */
   public double eval() {
       System.out.println("Error: eval Node");
       return 0;
   }
}

Binop.java

public class Binop extends Node {
  
   protected Node lChild, rChild;

   /**
   * @param l
   * @param r
   */
   public Binop(Node l, Node r) {
       lChild = l;
       rChild = r;
   }
  
  
}

Divide.java

public class Divide extends Binop {

   public Divide(Node l, Node r) {
       super(l, r);
   }

   public double eval() {
       return lChild.eval() / rChild.eval();
   }
  
   public String toString() {
       return "(" + lChild.toString() + " / " + rChild.toString() + ")";
   }
}

Minus.java

public class Minus extends Binop {
  
   public Minus(Node l, Node r) {
       super(l, r);
   }
  
   public double eval() {
       return lChild.eval() - rChild.eval();
   }
  
   public String toString() {
       return "(" + lChild.toString() + " - " + rChild.toString() + ")";
   }

}

Mult.java

public class Mult extends Binop {

   public Mult(Node l, Node r) {
       super(l, r);
   }

   public double eval() {
       return lChild.eval() * rChild.eval();
   }
  
   public String toString() {
       return "(" + lChild.toString() + " * " + rChild.toString() + ")";
   }
}

Const.java

public class Const extends Node {
  
   private double value;
  
   /**
   * Constructor to initialize the constant value for operation
   *
   * @param d constant value
   */
   public Const(double d) {
       value = d;
   }
  
   public double eval() {
       return value;
   }
  
   public String toString() {
       return "" + value;
   }
}

Plus.java

public class Plus extends Binop {
  
   public Plus(Node l, Node r) {
       super(l, r);
   }
  
   public double eval() {
       return lChild.eval() + rChild.eval();
   }
  
   public String toString() {
       return "(" + lChild.toString() + " + " + rChild.toString() + ")";
   }
}

Problems@Javadoc Declaration Console 3 <terminateds TestArithmetic [Java Application] CAProgram FilesJava jre1.3.0 201 1bin javaw.exe (Mar 4, 2019, 11:47:44 PM) (6.0 * 16.0) / (8.0-15.0)) -13.71 ((19.0-4.0) - (20.0 * 3.0)) = -45.0 ((2.0 + 1.0) / (17.0-1.0)) 0.19 ((9.0 + 12.0) + (2.0 * 1.0)) 23.0 ((5.8+13.0) (17.0 + 1.0))-324.0