String字符串包含运算符实现运算

   string aa = "(1+2)/3+(3+4)*5";
        DataTable dt = new DataTable();
        string b = dt.Compute(aa, "").ToString();
        Response.Write(b);

扩展：C#中DataTable中的Compute方法使用收集

java算法1：尚未验证 

import java.util.HashMap;
import java.util.Map;

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<Character, Operator> operators = new HashMap<Character, Operator>();
    
    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 double eval(double left, double right) {
                return left + right;
            }            
        };
    
    /**
     * 减法运算
     */
    public final static Operator SUBTRATION = new Operator('-', 100) {
            public double eval(double left, double right) {
                return left - right;
            }            
        };
    
    /**
     * 乘法运算
     */ 
    public final static Operator MULTIPLICATION = new Operator('*', 200) {
            public double eval(double left, double right) {
                return left * right;
            }            
        };
    
    /**
     * 除法运算
     */
    public final static Operator DIVITION = new Operator('/', 200) {
            public double eval(double left, double right) {
                return left / right;
            }            
        };
    
    /**
     * 冪运算
     */
    public final static Operator EXPONENT = new Operator('^', 300) {
            public double eval(double left, double right) {
                return Math.pow(left, right);
            }            
        };
        
    /**
     * 取模运算
     */
    public final static Operator MOD = new Operator('%', 200) {
            public double eval(double left, double right) {
                return left % right;
            }            
        };
    
    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);
        if(op != null) {
            return op.getPriority();
        }
        return 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) {
        if(str.length() > 1) {
            return false;
        }
        return 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) {
        if(str.length() > 1) {
            return null;
        }
        return 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 double eval(double left, double right); 
}

java算法2：尚未验证

public class Test {

    public static void main(String[] args) {
        String str = "40944.0501-3.2*100";
        Calculator cal = new Calculator();
        double d = cal.eval(str);
        System.out.println(d);
    }
}

public interface MathSymbol {
    
    /**
     * 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      = ' ';
}

import java.util.Stack;

public class Calculator implements MathSymbol {
    
    /**
     * 计算中缀表达式
     * @param expression
     * @return
     */
    public double eval(String expression) {
        String str = infix2Suffix(expression);
        //System.out.println(" Infix Expression: " + expression);
        //System.out.println("Suffix Expression: " + str);
        if(str == null) {
            throw new IllegalArgumentException("Expression is null!");
        }
        String[] strs = str.split("\s+");
        Stack<String> stack = new Stack<String>();
        for(int i = 0; i < strs.length; i++) {
            if(!Operator.isOperator(strs[i])) {
                stack.push(strs[i]);
            } else {
                Operator op = Operator.getInstance(strs[i]);
                double right = Double.parseDouble(stack.pop());
                double left = Double.parseDouble(stack.pop());
                double result = op.eval(left, right);
                stack.push(String.valueOf(result));
            }
        }
        return Double.parseDouble(stack.pop());
    }
    
    /**
     * 将中缀表达式转换为后缀表达式
     * @param expression
     * @return
     */
    public String infix2Suffix(String expression) {
        if(expression == null) {
            return null;
        }
        char[] chs = expression.toCharArray();
        Stack<Character> stack = new Stack<Character>();
        StringBuilder sb = new StringBuilder(chs.length);
        boolean appendSeparator = false;
        boolean sign = true;
        for(int i = 0; i < chs.length; i++) {
            char c = chs[i];
            if(c == BLANK) {
                continue;
            }
            // Next line is used output stack information.
            // System.out.printf("%-20s %s%n", stack, sb.toString());            
            if(appendSeparator) {
                sb.append(SEPARATOR);
                appendSeparator = false;
            }
            if(isSign(c) && sign) {
                sb.append(c);
                continue;
            }
            if(isNumber(c)) {
                sign = false;
                sb.append(c);
                continue;
            }            
            if(isLeftBracket(c)) {
                stack.push(c);
                continue;                
            }
            if(isRightBracket(c)) {
                sign = false;
                while(stack.peek() != LEFT_BRACKET) {
                    sb.append(SEPARATOR);
                    sb.append(stack.pop());
                }
                stack.pop();
                continue;
            }
            appendSeparator = true;
            if(Operator.isOperator(c)) {
                sign = true;
                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);
                    sb.append(stack.pop());
                }
                stack.push(c);                
            }
        }
        while(!stack.isEmpty()) {
            sb.append(SEPARATOR);
            sb.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) {
        if(c == NEGATIVE_SIGN || c == POSITIVE_SIGN) {
            return true;
        }
        return false;
    }
    
    /**
     * 判断某个字符是否为数字或者小数点
     * @param c
     * @return
     */
    private boolean isNumber(char c) {
        if((c >= '0' && c <= '9') || c == DECIMAL_POINT) {
            return true;
        }
        return false;
    }
    
    /**
     * 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;
    }
}