Help with a java program (binary tree)

[cioccolatina]

Hey guys, is there anyone who could help me..?

I have file ExpressionBinaryTree.java :

 
/** class ExpressionBinaryTree
*   uses a binary tree to represent binary expressions
*   does not implement BinaryTree - all iterators return String
*/
package foundations;
import java.util.*;
public class ExpressionBinaryTreeE implements Container {
    // Fields
    private SearchTreeNode root = null;
    private int size = 0;
    private String postfixString;
    // Constructors
    /** Create an empty expression tree
    */
    public ExpressionBinaryTreeE () {
    }
    /** Create and initialize an expression tree on infix
    */
    public ExpressionBinaryTreeE (String infix) {
        postfixString = (new FunctionEvaluation(infix)).postfix();
        buildExpressionTree();
    }
    // Commands
    /** Set a new value for infix
    *   updates postfixString and rebuilds expression tree
    */
    public void setInfixString (String infix) {
        postfixString = (new FunctionEvaluation(infix)).postfix();
        buildExpressionTree();
    }
    /** Set a new value for postfixString
    */
    public void setPostfixString (String postfix) {
        //  remove blanks then build expression tree
        //   left as an exercise
    }
    /** Remove all objects from the container if found
    */
    public void makeEmpty () {
        root = null;
    }
    // Queries
    /** Return a reference to the root
    */
    public SearchTreeNode root () {
        return root;
    }
    /** Return true if the container is empty
    */
    public boolean isEmpty () {
        return root == null;
    }
    /** Return the number of objects in the container
    *   postfixString has been trimmed
    */
    public int size () {
        return size;
    }
    /** Return the infix string on elements in the tree
    */
    public String traverseInorder () {
        // left as an exercise
        return "";
    }
    /** return the prefix string on elements in the tree
    */
    public String traversePreorder () {
        // left as an exercise
        return "";
    }
    /** Return the postfix on elements in the tree
    */
    public String traversePostorder () {
        //left as an exercise
        return "";
    }
    // Internal methods
    /** Build an expression tree from postfixString
    *   - use a Stack of SearchTreeNode
    *   throw NoSuchElementException for caught Stack error
    */
    private void buildExpressionTree () {
        // left as an exercise
    }
    private boolean isOperand (char ch) {
        // left as an exercise
        return false;
    }
    private boolean isOperator (char ch) {
        //left as an exercise
        return false;
    }
}
 

Also I have a supporting class (SearchTreeNode.java) for ExpressionBinaryTree and a test class ExpressionTest.java

** A test class for ExpressionBinaryTree (prefix input)
*/
import foundations.*;
import java.io.*;
public class ExpressionTest{
    public static void main(String[] args) throws IOException {
        ExpressionBinaryTreeE expr = new ExpressionBinaryTreeE("a+b/(c-d)-e");
        if (!expr.isEmpty()){
            System.out.println("The number of terms in the tree is: " + expr.size());
            System.out.println("Equiv infix string is:   " + expr.traverseInorder());
            System.out.println("Equiv prefix string is:  " + expr.traversePreorder());
            System.out.println("Equiv postfix string is: " + expr.traversePostorder());
        }
        System.out.println("Test makeEmpty()");
        expr.makeEmpty();
        System.out.println("The number of terms in the tree is: " + expr.size() + "\n");
        expr.setInfixString("a*b/(c-d)*e");//"a*b-(c-d*e)+f/(g-h)" or "a+b-(c-d*e)"
        if (!expr.isEmpty()){
            System.out.println("The number of terms in the tree is: " + expr.size());
            System.out.println("Equiv infix string is:   " + expr.traverseInorder());
            System.out.println("Equiv prefix string is:  " + expr.traversePreorder());
            System.out.println("Equiv postfix string is: " + expr.traversePostorder());
        }
        System.out.println("Test makeEmpty()");
        expr.makeEmpty();
        System.out.println("The number of terms in the tree is: " + expr.size() + "\n");
        expr.setInfixString("a+(b-c)-d/e");//"a*b-(c-d*e)+f/(g-h)" or "a+b-(c-d*e)"
        if (!expr.isEmpty()){
            System.out.println("The number of terms in the tree is: " + expr.size());
            System.out.println("Equiv infix string is:   " + expr.traverseInorder());
            System.out.println("Equiv prefix string is:  " + expr.traversePreorder());
            System.out.println("Equiv postfix string is: " + expr.traversePostorder());
        }
        System.out.println("Test makeEmpty()");
        expr.makeEmpty();
        System.out.println("The number of terms in the tree is: " + expr.size() + "\n");
        expr.setInfixString("a*b-(c-d*e)+f/(g-h)");//"a*b-(c-d*e)+f/(g-h)" or "a+b-(c-d*e)"
        if (!expr.isEmpty()){
            System.out.println("The number of terms in the tree is: " + expr.size());
            System.out.println("Equiv infix string is:   " + expr.traverseInorder());
            System.out.println("Equiv prefix string is:  " + expr.traversePreorder());
            System.out.println("Equiv postfix string is: " + expr.traversePostorder());
        }
        System.out.println("Test makeEmpty()");
        expr.makeEmpty();
        System.out.println("The number of terms in the tree is: " + expr.size() + "\n");
        BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
        String postfix = "";
        do {
            System.out.print("Enter a postfix string: ");
            postfix = keyboard.readLine();
            expr.setPostfixString(postfix);
            if (!expr.isEmpty()){
                System.out.println("The number of terms in the tree is: " + expr.size());
                System.out.println("Equiv infix string is:   " + expr.traverseInorder());
                System.out.println("Equiv prefix string is:  " + expr.traversePreorder());
                System.out.println("Equiv postfix string is: " + expr.traversePostorder());
            }
            System.out.println("Test makeEmpty()");
            expr.makeEmpty();
            System.out.println("The number of terms in the tree is: " + expr.size() + "\n");
        } while (postfix.length() >= 3);
    }
}
 
 

Batch file Go. bat compiles all source files and runs the test class:

javac ExpressionTest.java
java ExpressionTest
del *.class
del foundations\*.class
 

I am required to complete the details for class ExpressionBinaryTree. Additional statements may be added to class ExpressionTest to expand on the testing performed.

Any ideas....?

[JosAH]

I am required to complete the details for class ExpressionBinaryTree. Additional statements may be added to class ExpressionTest to expand on the testing performed.

Any ideas....?

Yup, I'd say that additional statements have to be added to that class because
as it is now it is an empty class, i.e. there are no useful things in it at all.

You have to write an entire parser; an AST (Abstract Syntax Tree) and a few
methods that transfer that AST to postfix, prefix and infix form. We won't do
it for you but if you're stuck we're very willing to help so get going.

kind regards,

Jos

[cioccolatina]

Thank You Jos!! :) Helped me a lot.