JAVA编程从一个资料中读取公式，计算每一个公式的结果并输出

Exception in thread "main" java.util.NoSuchElementException    at java.util.LinkedList.remove(LinkedList.java:788)    at java.util.LinkedList.removeFirst(LinkedList.java:134)    at java.util.LinkedList.pop(LinkedList.java:601)    at Temp.OPText.main(OPText.java:64)

//主类 import java.util.Deque;import java.util.LinkedList;import java.util.List;import java.util.regex.Matcher;import java.util.regex.Pattern;public class OPText {    public static void main(String[] args) {        String expression = "2+2+(8-2)/3";// 要计算的表达式        List list = new LinkedList();        // 正则式        Pattern entryOfExpression = Pattern.compile("[0-9]+(\\.[0-9]+)? |\\( |\\) |\\+ |- |\\* |/");         Deque stack = new LinkedList();// 栈        Matcher m = entryOfExpression.matcher(expression);        while (m.find()) {            // 提取语素            String nodeString = expression.substring(m.start(), m.end());            if (nodeString.matches("[0-9].*")) {                list.add(Double.valueOf(nodeString));// 如果是数字直接送入列表            } else {                OPNode opn = new OPNode(nodeString);// 如果是运算符                int peekLevel = (stack.peek() == null) ? 0 : ((OPNode)stack.peek()).level;                if (opn.level >= peekLevel) {                    stack.push(opn);// 新的运算符比旧的优先级别高则入栈                } else {                    if (opn.level == -1) {                        OPNode temp = (OPNode) stack.pop();                        while (temp.level != -3) {// 如果为"("则一直出栈一直到")"                            list.add(temp);                            System.out.println(nodeString);                            temp = (OPNode)stack.pop();                        }                    } else if (opn.level == -3) {                        stack.push(opn);                    } else {// 如果新运算符比栈顶运算符底则一直出栈                        OPNode temp = (OPNode) stack.pop();                        while (temp.level > opn.level) {                            list.add(temp);                            if (stack.isEmpty()) {                                break;                            }                            temp = (OPNode)stack.pop();                        }                        stack.push(opn);                    }                }            }        }        OPNode temp = null;        while (!stack.isEmpty()) {            temp = (OPNode)stack.pop();            list.add(temp);        }// 后续表达式计算        stack.clear();        for (Object o : list) {            if (o instanceof Double) {                stack.push(o);// 为数字入栈            } else {                double op2 = ((Double)stack.pop()).doubleValue();                double op1 = ((Double)stack.pop()).doubleValue();                switch (((OPNode) o).op) {                case '+':                    stack.push(op1 + op2);                    break;                case '-':                    stack.push(op1 - op2);                    break;                case '*':                    stack.push(op1 * op2);                    break;                case '/':                    stack.push(op1 / op2);                    break;                }            }        }        System.out.println("结果为:" + stack.pop());    }}

public class OPNode {    char op;// 运算符号     int level;// 优先级     //设置优先级     public OPNode(String op) {         this.op = op.charAt(0);         if (op.equals("+") || op.equals("-")) {             this.level = 1;         }else if (op.equals("*") || op.equals("/")) {             this.level = 2;         }else if (op.equals("(")) {             this.level = -3;         }else {             this.level = -1;         }     }  }