软件体系结构的第二次实验（解释器风格与管道过滤器风格

import java.util.*;

public class Test {

        public static void main(String[] args) {
            while(true){
                Scanner scanner = new Scanner(System.in);
                System.out.print("calc > ");
                String text = scanner.nextLine();
                if (analyzer(text))
                    System.out.println(calculate(toSuffix(text)));
                else
                    System.out.println("输入有误，请重新输入！！");
            }

        }

        //验证是否有空格
        static List<Object> toSuffix(String s) {
            Map<String, Integer> map = new HashMap<String, Integer>();
            map.put("+", 0);
            map.put("-", 0);
            map.put("*", 1);
            map.put("/", 1);
            List<Object> list = new ArrayList<Object>();
            s = s.replace(" ", "");
            String[] number = s.split("[^\\d]");
            String[] operator = s.split("\\d+");
            Stack<String> stack = new Stack<String>();
            for (int i = 0; i < number.length; i++) {
                if (operator[i].length() != 0) {
                    while (!stack.isEmpty()
                            && map.get(operator[i]) <= map.get(stack.peek())) {
                        list.add(stack.pop());
                    }
                    stack.push(operator[i]);
                }
                list.add(Double.parseDouble(number[i]));
            }
            while (!stack.isEmpty()) {
                list.add(stack.pop());
            }
            return list;
        }

        //计算
        static double calculate(List<Object> list) {
            Stack<Double> stack = new Stack<Double>();
            for (Object obj : list) {
                if (obj instanceof Double) {
                    stack.push((Double) obj);
                } else {
                    double b = stack.pop();
                    double a = stack.pop();
                    if (obj.equals("+"))
                        stack.push(a + b);
                    if (obj.equals("-"))
                        stack.push(a - b);
                    if (obj.equals("*"))
                        stack.push(a * b);
                    if (obj.equals("/"))
                        stack.push(a / b);
                }
            }
            return stack.pop();
        }

        private static boolean analyzer(String text) {

            String[] signs = {"+", "-", "*", "/"};
            boolean isRight = true;
            //语法分析
            boolean haveSign = false;
            for (String sign : signs) {
                //是否包含运算符
                if (text.contains(sign)) {
                    haveSign = true;
                }
                //是否有连续的运算符
                if (text.contains(sign + sign)) {
                    isRight = false;
                }
                //首尾是否为运算符
                if ( text.indexOf(sign) == 0 || text.lastIndexOf(sign) == text.length() - 1) {
                    isRight = false;
                }
            }
            isRight = isRight && haveSign;
            return isRight;
        }
}