从控制台读取数据

public static String getString() throws IOException {
        InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        String s = br.readLine();
        return s;
    }

 

public static void main(String[] args) throws IOException {
        String str_input;
        double f_output;
       
        while (true) {
            System.out.print("输入表达式: ");
            System.out.flush();
           
            str_input = getString();
            if (str_input.equals("")) {
                break;
            }
           
            Calculator calculator = new Calculator();
           
            //以下对输入字符串做规则处理
            str_input = calculator.checkExpression(str_input);
            if (str_input.equals("")) {
                System.out.println("   表达式出错  ");
            }
           
            //以下对输入字符串做表达式转换
            Vector<String> v_compute = calculator.getExpression(str_input);
            //以下进行后缀表达式转换
            Vector<String> v_tmp_prefix = calculator.transformPrefix(v_compute);       
            //以下进行后缀表达式运算
            f_output = calculator.evaluatePrefix(v_tmp_prefix);
           
            System.out.println("结果 = " + f_output);
           
        }