import java.util.ArrayList; import java.util.HashSet; import java.util.Scanner; //Input is optional. //Default input : "(3+5*(2+3)-1)/3" class ExpressionData { private String Expr; static HashSet Operators = new HashSet<>(4,2f); static { Operators.add('*');Operators.add('/'); Operators.add('+');Operators.add('-'); } public ExpressionData(String expr) { System.out.println("expr : " + expr); while(expr.indexOf('(')!=-1 && expr!=null) expr = BracketHandler(expr); System.out.println(Evaluate(expr)); Expr = expr; } public static double Evaluate(String Expr) { ArrayList OperatorList = new ArrayList<>(5); ArrayList OperandList = new ArrayList<>(); Expr = Expr.replaceAll(" ", ""); try { int first = 0 ; for(int i = (Expr.charAt(first)=='-' ? 1 : 0) ; i < Expr.length() ; i++){ if(Operators.contains(Expr.charAt(i))){ OperatorList.add(Expr.charAt(i)); OperandList.add(Double.parseDouble(Expr.substring(first,i))); first = i+1; } } OperandList.add(Double.valueOf(Expr.substring(first,Expr.length()))); } catch (Exception e){ System.out.println("Invalid Expression"); } double result = 0; try { //for evaluation based on priority. Line 44-65 int index; for(char a : new char[]{'/', '*', '+','-'}) while((index = OperatorList.indexOf(a))!=-1){ OperatorList.remove(index); switch (a){ case '/': OperandList.add(index,OperandList.get(index) / OperandList.get(index+1)); break; case '*': OperandList.add(index,OperandList.get(index) * OperandList.get(index+1)); break; case '+': OperandList.add(index,OperandList.get(index) + OperandList.get(index+1)); break; case '-': OperandList.add(index,OperandList.get(index) - OperandList.get(index+1)); break; } OperandList.remove(index+1); OperandList.remove(index+1); } result = OperandList.get(0); //Without Priority just left to right scan. Line : 68 - 86. /* result = OperandList.get(0); for (int i = 0; i < OperatorList.size(); i++) { double b = OperandList.get(i + 1); switch (OperatorList.get(i)) { case '/': result /= b; break; case '*': result *= b; break; case '+': result += b; break; case '-': result -= b; break; } } */ } catch (Exception e){ System.out.println("Invalid Expression"); } return result; } private String BracketHandler(String expr) { int count = 0; for(int i = 0 ; i

Expression Evalution