such as \"(((3.2 * 25) - (4.3 / 2)) + 9.3)\", where each operand is a positive r

Question

                    such as "(((3.2 * 25) - (4.3 / 2)) + 9.3)", where each operand is a positive real number, integer, or an expression,                 

                    and an operator is +, -, *, or /, with two operands and a pair of parentheses indicating the order of operations.                 

                    2. Build an expression tree from either a given (double or int) number alone, or a given (char) operator plus two sub-trees.                 

                    3. Evaluate a given expression tree.                 

                    4. Convert a given expression tree into a String, according to a given traversal order (preorder, inorder, or postorder).
                    hint: you need to show 3 lines one for each traversal                 

                    please write full java source

Explanation / Answer

import java.util.StringTokenizer; public class TokenExample {   private static final String OPERATORS = "+-*/()";   private static boolean isOperator(char ch) {   return OPERATORS.indexOf(ch) != -1;   }   public static void main(String[] args) {   String infix="3.1+1.2"; StringBuilder postfix = new StringBuilder();   StringTokenizer infixTokens = new StringTokenizer(infix, OPERATORS+" ", true); while (infixTokens.hasMoreTokens()) {   String nextToken = infixTokens.nextToken();   char firstChar = nextToken.charAt(0);   if (Character.isJavaIdentifierStart(firstChar)   || Character.isDigit(firstChar)) { postfix.append(nextToken); postfix.append(' '); System.out.println("real numbers: "+postfix);   }else if (isOperator(firstChar)) {   System.out.println("operator:"+firstChar);   } }   } }

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