Java使用逆波兰表达式算法制作的表达式计算器

Java使用逆波兰表达式算法制作的表达式计算器

package com.infogrid.g2b;   
  
import java.util.HashMap;   
import java.util.Map;   
  
  
public class Op {   
       
    private static final Map<String,Integer> ops = new HashMap<String, Integer>();   
    static{   
        ops.put("+",10);   
        ops.put("-",10);   
        ops.put("*",20);   
        ops.put("/",20);   
        ops.put("%",20);   
        ops.put("(",100);   
        ops.put(")",100);   
    }   
       
    public static boolean isSign(String sign1){   
        Integer s = ops.get(sign1);   
        if(s==null)   
            return false;   
        else  
            return true;   
    }   
       
    public static int compare(String sign1,String sign2){   
        Integer p1 = ops.get(sign1);   
        Integer p2 = ops.get(sign2);   
        if(p1==null)   
            throw new IllegalArgumentException("符号："+sign1+"不存在！");   
        if(p2==null)   
            throw new IllegalArgumentException("符号："+sign2+"不存在！");   
        return p1-p2;   
    }   
       
    public static Object cal(Object x,Object y,String sign){   
        Double a=0.0,b=0.0;   
        a = Double.valueOf(x+"");   
        b = Double.valueOf(y+"");   
        if(sign.equals("+"))   
            return a+b;   
        if(sign.equals("-"))   
            return a-b;   
        if(sign.equals("*"))   
            return a*b;   
        if(sign.equals("/"))   
            return a/b;   
        if(sign.equals("%"))   
            return a%b;   
        throw new IllegalArgumentException("操作符不合法！");   
    }   
}  
package com.infogrid.g2b;   
  
import java.util.ArrayList;   
import java.util.List;   
import java.util.Stack;   
  
public class Calculator {   
       
    private List list = new ArrayList();   
    private Stack stack = new Stack();   
       
       
    private List resolveExpr(String exp){      
        String opert=exp.replaceAll("\\d*\\.\\d+?", "");   
        List list=new ArrayList();      
        int pidx=-1;      
        for(int i=0;i<opert.length();i++){ String p=opert.substring(i, i+1); pidx=exp.indexOf(p); if(exp.substring(0,pidx).trim().length()!=0){ list.add(exp.substring(0, pidx)); } list.add(exp.substring(pidx, pidx+1)); exp=exp.substring(pidx+1); } if(exp.length()>0){      
            list.add(exp);      
        }      
        return list;      
    }      
       
    private void dealSign(String s){   
        if(stack.size()==0){   
            stack.push(s);   
            return;   
        }   
        String ps = stack.pop();   
        if(Op.compare(s, ps)>0||ps.equals("(")){   
            if(s.equals(")")){   
                list.add(ps);   
                while(stack.size()>0){   
                    ps = stack.pop();   
                    if(ps.equals("("))   
                        break;   
                    list.add(ps);   
                }   
            }else{   
                stack.push(ps);   
                stack.push(s);   
            }   
        }else{   
            list.add(ps);   
            dealSign(s);   
        }   
    }   
       
    private void dealVar(String s){   
        list.add(s);   
    }   
       
    private Double getResult(){   
        for(String s:list){   
            if(!Op.isSign(s)){   
                stack.push(s);   
                continue;   
            }   
            Object a = 0,b = 0;   
            if(stack.size()>0)   
                b = stack.pop();   
            if(stack.size()>0)   
                a = stack.pop();   
            stack.push(Op.cal(a, b, s)+"");   
        }   
        return Double.valueOf(stack.pop());   
    }   
       
    public Double calculate(String expression){   
        List ss = resolveExpr(expression);   
        for(String s:ss){   
            if(Op.isSign(s)){   
                dealSign(s);   
            }else{   
                dealVar(s);   
            }   
        }   
        while(stack.size()>0){   
            list.add(stack.pop());   
        }   
        System.out.println(list);   
           
        return getResult();   
    }   
       
       
  
       
    public static void main(String[] args) {   
        System.out.println(new Calculator().calculate("1.5+2.1+((4/2)-6/((2+1)*2))+6%4"));   
    }   
}