How to implement mathematical expression in Java?

Any ideas to create this java program?

• Create a java program that reads in one line as a fully parenthesized infix expression and builds a binary expression tree. It should repeat this until a blank line is entered. The tokens, including numbers, parentheses, and four operators ( +, -, *, /) are separated by spaces. Hints on the programming: 1. Implement a BTNode class that represents a node in a binary tree. Each node holds three kinds of data: an element, a reference to the left child, and a reference to the right child. You are going to use this class to instantiate nodes in the expression tree. Since a node can hold a number or an operator, it is appropriate to use Object to define the element. 2. Implement a generic Stack class. You are going to use the Stack class to instantiate two Stack objects: one in BTNode type for the nodes in the expression tree, and one for parentheses in Character for extra credits. 3. Implement BinExprTree class. The only instance field in this class is a reference to the root node of an expression tree. In this class, you need to implement various methods.

• Answer:

  i did this for my lab i can give you the stub... creating a BTNode tree class is easy.. the class will have 3 instance variables. String myItem BTNode myRight BTNode myLeft if (expr.charAt (0) != '(') { ____; // this means its not a parenthesed expression } else { // expr is a parenthesized expression. // Strip off the beginning and ending parentheses, // find the main operator (an occurrence of + or * not nested // in parentheses, and construct the two subtrees. int nesting = 0; int opPos = 0; for (int k=1; k<expr.length()-1; k++) { ____ ; // you supply the missing code // find the position of the operator middle operator // that is the same thing is when nesting = 0 // so you set opPos to k; } String opnd1 = expr.substring (1, opPos); String opnd2 = expr.substring (opPos+1, expr.length()-1); String op = expr.substring (opPos, opPos+1); System.out.println ("expression = " + expr); System.out.println ("operand 1 = " + opnd1); System.out.println ("operator = " + op); System.out.println ("operand 2 = " + opnd2); System.out.println ( ); //This is test to see if you did it right.. ____; //when you get here recursively call the constructor with left and right expression //should look like myLeft = new BTNode(opnd1); like myLeft = new BTNode(opnd2); } if you have any questions feel free to email me [email protected]