使用java处理字符串公式运算的方法

public class FormulaTest {
     @Test
     public void testFormula() {
         //基础数据
         Map values = new HashMap();
         values.put("dddd", BigDecimal.valueOf(56d));

         //需要依赖的其他公式
         Map formulas = new HashMap();
         formulas.put("eeee", "#{dddd}*20");

         //需要计算的公式
         String expression = "#{eeee}*-12+13-#{dddd}+24";

         BigDecimal result = FormulaParser.parse(expression, formulas, values);
         Assert.assertEquals(result, BigDecimal.valueOf(-13459.0));
     }
 }

public class FormulaParser {
     /**
      * 匹配变量占位符的正则表达式
      */
     private static Pattern pattern = Pattern.compile("\\#\\{(.+?)\\}");

     /**
      * 解析公式，并执行公式计算
      *
      * @param formula
      * @param formulas
      * @param values
      * @return
      */
     public static BigDecimal parse(String formula, Map formulas, Map values) {
         if (formulas == null)formulas = Collections.emptyMap();
         if (values == null)values = Collections.emptyMap();
         String expression = finalExpression(formula, formulas, values);
         return new Calculator().eval(expression);
     }

     /**
      * 解析公式，并执行公式计算
      *
      * @param formula
      * @param values
      * @return
      */
     public static BigDecimal parse(String formula, Map values) {
         if (values == null)values = Collections.emptyMap();
         return parse(formula, Collections. emptyMap(), values);
     }

     /**
      * 解析公式，并执行公式计算
      *
      * @param formula
      * @return
      */
     public static BigDecimal parse(String formula) {
         return parse(formula, Collections. emptyMap(), Collections. emptyMap());
     }

     /**
      * 将所有中间变量都替换成基础数据
      *
      * @param expression
      * @param formulas
      * @param values
      * @return
      */
     private static String finalExpression(String expression, Map formulas, Map values) {
         Matcher m = pattern.matcher(expression);
         if (!m.find())return expression;

         m.reset();

         StringBuffer buffer = new StringBuffer();
         while (m.find()) {
             String group = m.group(1);
             if (formulas != null && formulas.containsKey(group)) {
                 String formula = formulas.get(group);
                 m.appendReplacement(buffer, '(' + formula + ')');
             } else if (values != null && values.containsKey(group)) {
                 BigDecimal value = values.get(group);
                 m.appendReplacement(buffer,value.toPlainString());
             }else{
                 throw new IllegalArgumentException("expression '"+expression+"' has a illegal variable:"+m.group()+",cause veriable '"+group+"' not being found in formulas or in values.");
             }
         }
         m.appendTail(buffer);
         return finalExpression(buffer.toString(), formulas, values);
     }
 }

public class Calculator{
     private static Log logger = LogFactory.getLog(Calculator.class);

     /**
      * 左括号
      */
     public final static char LEFT_BRACKET = '(';

     /**
      * 右括号
      */
     public final static char RIGHT_BRACKET = ')';

     /**
      * 中缀表达式中的空格，需要要忽略
      */
     public final static char BLANK = ' ';

     /**
      * 小数点符号
      */
     public final static char DECIMAL_POINT = '.';

     /**
      * 负号
      */
     public final static char NEGATIVE_SIGN = '-';

     /**
      * 正号
      */
     public final static char POSITIVE_SIGN = '+';

     /**
      * 后缀表达式的各段的分隔符
      */
     public final static char SEPARATOR = ' ';

     /**
      * 解析并计算表达式
      *
      * @param expression
      * @return
      */
     public BigDecimal eval(String expression) {
         String str = infix2Suffix(expression);
         logger.info("Infix Expression: " + expression);
         logger.info("Suffix Expression: " + str);
         if (str == null) {
             throw new IllegalArgumentException("Infix Expression is null!");
         }
         return evalInfix(str);
     }

     /**
      * 对后缀表达式进行计算
      *
      * @param expression
      * @return
      */
     private BigDecimal evalInfix(String expression) {
         String[] strs = expression.split("\\s+");
         Stack stack = new Stack();
         for (int i = 0; i              if (!Operator.isOperator(strs[i])) {
                 stack.push(strs[i]);
             } else {
                 Operator op = Operator.getInstance(strs[i]);
                 BigDecimal right =new BigDecimal(stack.pop());
                 BigDecimal left =new BigDecimal(stack.pop());
                 BigDecimal result = op.eval(left, right);
                 stack.push(String.valueOf(result));
             }
         }
         return new BigDecimal(stack.pop());
     }

     /**
      * 将中缀表达式转换为后缀表达式

      * 具体算法规则 81      * 1)计算机实现转换： 将中缀表达式转换为后缀表达式的算法思想：
      *     开始扫描；
      *         数字时，加入后缀表达式；
      *         运算符：
      *  a.若为 '('，入栈；
      *  b.若为 ')'，则依次把栈中的的运算符加入后缀表达式中，直到出现'('，从栈中删除'(' ；
      *  c.若为 除括号外的其他运算符 ，当其优先级高于栈顶运算符时，直接入栈。否则从栈顶开始，依次弹出比当前处理的运算符优先级高和优先级相等的运算符，直到一个比它优先级低的或者遇到了一个左括号为止。
      *  ·当扫描的中缀表达式结束时，栈中的的所有运算符出栈；　
      *
      * @param expression
      * @return
      */
     public String infix2Suffix(String expression) {
         if (expression == null) return null;

         Stack stack = new Stack();

         char[] chs = expression.toCharArray();
         StringBuilder sb = new StringBuilder(chs.length);

         boolean appendSeparator = false;
         boolean sign = true;
         for (int i = 0; i              char c = chs[i];

             // 空白则跳过
             if (c == BLANK)continue;

             // Next line is used output stack information.
             // System.out.printf("%-20s %s%n", stack, sb.toString());

             // 添加后缀表达式分隔符
             if (appendSeparator) {
                 sb.append(SEPARATOR);
                 appendSeparator = false;
             }

             if (isSign(c) && sign) {
                 sb.append(c);
             } else if (isNumber(c)) {
                 sign = false;// 数字后面不是正号或负号，而是操作符+-
                 sb.append(c);
             } else if (isLeftBracket(c)) {
                 stack.push(c);
             } else if (isRightBracket(c)) {
                 sign = false;

                 // 如果为)，则弹出(上面的所有操作符，并添加到后缀表达式中，并弹出(
                 while (stack.peek() != LEFT_BRACKET) {
                     sb.append(SEPARATOR).append(stack.pop());
                 }
                 stack.pop();
             } else {
                 appendSeparator = true;
                 if (Operator.isOperator(c)) {
                     sign = true;

                     // 若为(则入栈
                     if (stack.isEmpty() || stack.peek() == LEFT_BRACKET) {
                         stack.push(c);
                         continue;
                     }
                     int precedence = Operator.getPrority(c);
                     while (!stack.isEmpty() && Operator.getPrority(stack.peek()) >= precedence) {
                         sb.append(SEPARATOR).append(stack.pop());
                     }
                     stack.push(c);
                 }
             }
         }
         while (!stack.isEmpty()) {
             sb.append(SEPARATOR).append(stack.pop());
         }
         return sb.toString();
     }

     /**
      * 判断某个字符是否是正号或者负号
      *
      * @param c
      * @return
      */
     private boolean isSign(char c) {
         return (c == NEGATIVE_SIGN || c == POSITIVE_SIGN);
     }

     /**
      * 判断某个字符是否为数字或者小数点
      *
      * @param c
      * @return
      */
     private boolean isNumber(char c) {
         return ((c >= '0' && c <= '9') || c == DECIMAL_POINT);
     }

     /**
      * 判断某个字符是否为左括号
      *
      * @param c
      * @return
      */
     private boolean isLeftBracket(char c) {
         return c == LEFT_BRACKET;
     }

     /**
      * 判断某个字符是否为右括号
      *
      * @param c
      * @return
      */
     private boolean isRightBracket(char c) {
         return c == RIGHT_BRACKET;
     }

View Code
 public abstract class Operator {
     /**
      * 运算符
      */
     private char operator;

     /**
      * 运算符的优先级别，数字越大，优先级别越高
      */
     private int priority;

     private static Map operators = new HashMap();

     private Operator(char operator, int priority) {
         setOperator(operator);
         setPriority(priority);
         register(this);
     }

     private void register(Operator operator) {
         operators.put(operator.getOperator(), operator);
     }

     /**
      * 加法运算
      */
     public final static Operator ADITION = new Operator('+', 100) {
         public BigDecimal eval(BigDecimal left, BigDecimal right) {
             return left.add(right);
         }
     };

     /**
      * 减法运算
      */
     public final static Operator SUBTRATION = new Operator('-', 100) {
         public BigDecimal eval(BigDecimal left, BigDecimal right) {
             return left.subtract(right);
         }
     };

     /**
      * 乘法运算
      */
     public final static Operator MULTIPLICATION = new Operator('*', 200) {
         public BigDecimal eval(BigDecimal left, BigDecimal right) {
             return left.multiply(right);
         }
     };

     /**
      * 除法运算
      */
     public final static Operator DIVITION = new Operator('/', 200) {
         public BigDecimal eval(BigDecimal left, BigDecimal right) {
             return left.divide(right);
         }
     };

     /**
      * 冪运算
      */
     public final static Operator EXPOnENT= new Operator('^', 300) {
         public BigDecimal eval(BigDecimal left, BigDecimal right) {
             return left.pow(right.intValue());
         }
     };

     public char getOperator() {
         return operator;
     }

     private void setOperator(char operator) {
         this.operator = operator;
     }

     public int getPriority() {
         return priority;
     }

     private void setPriority(int priority) {
         this.priority = priority;
     }

     /**
      * 根据某个运算符获得该运算符的优先级别
      *
      * @param c
      * @return 运算符的优先级别
      */
     public static int getPrority(char c) {
         Operator op = operators.get(c);
         return op != null ? op.getPriority() : 0;
     }

     /**
      * 工具方法，判断某个字符是否是运算符
      *
      * @param c
      * @return 是运算符返回 true，否则返回 false
      */
     public static boolean isOperator(char c) {
         return getInstance(c) != null;
     }

     public static boolean isOperator(String str) {
         return str.length() > 1 ? false : isOperator(str.charAt(0));
     }

     /**
      * 根据运算符获得 Operator 实例
      *
      * @param c
      * @return 从注册中的 Operator 返回实例，尚未注册返回 null
      */
     public static Operator getInstance(char c) {
         return operators.get(c);
     }

     public static Operator getInstance(String str) {
         return str.length() > 1 ? null : getInstance(str.charAt(0));
     }

     /**
      * 根据操作数进行计算
      *
      * @param left
      *            左操作数
      * @param right
      *            右操作数
      * @return 计算结果
      */
     public abstract BigDecimal eval(BigDecimal left, BigDecimal right);