一年前写的，主要看看核心算法吧。。。细节可能会有点问题
// 1. 将读到的数字依次放入数字栈
// 2. 读出的符号的优先级若不大于符号栈顶元素的优先级，则将栈顶元素弹出参与运算。
// 3. 括号起隔离作用
// 4. 优先级 '#' < +,- < *,/

public class ExpressionCalculation
{
    private String InfixationExpression;
    private myStack1 EStack;
    
    public ExpressionCalculation()
    {
        this("1*2+(3-5/4)*6");    
    }
    
    public ExpressionCalculation( String expression )
    {
        // 表达式后加自定义结束符'#'
        InfixationExpression = expression+'#';
        EStack = new myStack1();
        System.out.print(expression);    
    }
    
    public void ChangeToSuffixExpression()
    {     
        myStack TStack = new myStack();    
        TStack.push("#");
        
        int i = 0;
        String number = "";
        while( i < InfixationExpression.length() )
        {
            if( (InfixationExpression.charAt(i) > 47) && (InfixationExpression.charAt(i) < 58) )
            {
                number += InfixationExpression.charAt(i);    
            }
            else
            {
                if(number != "")
                {
                    EStack.push(Integer.parseInt(number));
                    number = "";
                }
                // 如果符号为+，-,若栈中符号优先级高，则将栈中取出运算
                if( (InfixationExpression.charAt(i) == '+') || (InfixationExpression.charAt(i) == '-') )
                {
                    while( (TStack.top() != "#") && (TStack.top() != "(") )
                    {
                        String t = TStack.top();
                        Calculate(t);
                        TStack.pop();
                    }
                    TStack.push(InfixationExpression.charAt(i)+"");
                }
                //遇结束符，则将符号栈中符号全部取出运算
                else if(InfixationExpression.charAt(i) == '#')
                {
                    while(TStack.getLength() > 0)
                    {
                        String t = TStack.top();
                        Calculate(t);
                        TStack.pop();    
                    }    
                }
                
                else if( (InfixationExpression.charAt(i) == '*') || (InfixationExpression.charAt(i) == '/') )
                {
                    while( (TStack.top() == "*") || (TStack.top() == "/") )
                    {
                        String t = TStack.top();
                        Calculate(t);
                        TStack.pop();
                    }
                    TStack.push(InfixationExpression.charAt(i)+"");
                }
                else if(InfixationExpression.charAt(i) == '(')
                {
                    TStack.push("(");    
                }
                else if(InfixationExpression.charAt(i) == ')')
                {
                    while(!TStack.top().equals("("))
                    {
                        String t = TStack.top();
                        Calculate(t);
                        TStack.pop();
                    }
                    TStack.pop();    
                }
            }
            i ++;
        }
    }
    
    private void Calculate( String op )
    {
        if( op.equals("#") )
        {
            int result = EStack.top();
            System.out.println(" = " + result);
        }
        else
        {
            int num2 = EStack.top();
            EStack.pop();
            int num1 = EStack.top();
            EStack.pop();

            if(op.equals("+"))
            {
                EStack.push( num1+num2 );
            }
            else if(op.equals("-"))
            {
                EStack.push( num1-num2 );    
            }
            else if(op.equals("*"))
            {
                EStack.push( num1*num2 );    
            }
            else if(op.equals("/"))
            {
                EStack.push( num1/num2 );    
            }
            else
            {
                System.out.println("Error!");    
            }            
        }    
    }
    
    public static void main(String args[])
    {
        ExpressionCalculation ec = new ExpressionCalculation();
        ec.ChangeToSuffixExpression();    
    }
}

谢谢各位了