逆波兰式生成与表达式合法性判定

package com.wangshitong;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Stack;

public class Nbls {
static String nbls="" ,expression="";;
//根据传过来的操作符确定优先级（传过来的操作符一定得有效）
private static String get(char a,char b){
   if((b == '('&& a != ')')||(a=='(' && b != ')') || (a=='|' && b != '|' && b != ')') ||((a=='*'|| a=='/') && (b=='+' || b=='-'))){
    return ">";
   }else if(b=='(' && a==')'){
    return "=";
   }else if(b==')' && a=='('){
    return "出错：右括号后不能跟左括号";
   }else return "<";
}
private static boolean p(char a){
   if(a != '+' && a != '-'&& a != '*' && a != '/' && a != '|' && a != '(' && a != ')'){
    return false;
   }
   return true;
}
//判断操作符是否有效，将有效的操作符传至get(char,char)函数与确定优先级
private static String panduan(char a,char b){
   String str= "";
   if(!p(a)){
    str = a + "为非法操作符,";

   }
   if(!p(b)){
    str = str + b + "为非法操作符";
   }
   if(!"".equals(str)){
    return str;
   }
   return get(a, b);
}
private static void ta(Stack<String> s){
   char b= s.lastElement().charAt(0);
   System.out.println("当前栈顶为：" + b);
   if(b=='('){System.out.println(s.pop() + "退栈");return;}
   else{
    if(s.isEmpty())System.out.println("ERROR");
    else {String c= s.pop();System.out.println(c + "退栈,并输出！");nbls += c;}
    ta(s);
   }
}
private static void te(Stack<String> s,char a){
   if(s.isEmpty()){
    s.push(a+"");System.out.println("栈为空,所以" + a +"进栈");return;
   }else{
    String b=panduan(a,s.lastElement().charAt(0));
    System.out.println("当前运算符为："+a+",栈顶运算符为："+s.lastElement().charAt(0));
    System.out.println("当前运算符与栈顶运算符优先级比较：" + b);
    if(">".equals(b)){
     s.push(a+"");System.out.println("当前运算符高于栈顶运算符优先级,所以" + a +"入栈");return;
    }else{
     if(a!=')'){