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import java.util.ArrayList;import java.util.Stack; /** *  * @author arthur * */public class Calculate {		public ArrayList
   
     getStringList(String str){		ArrayList
    
      result = new ArrayList
     
      ();		String num = "";		for (int i = 0; i < str.length(); i++) {			if(Character.isDigit(str.charAt(i))){				num = num + str.charAt(i);			}else{				if(num != ""){					result.add(num);				}				result.add(str.charAt(i) + "");				num = "";			}		}		if(num != ""){			result.add(num);		}		return result;	}		/**	 * 将中缀表达式转化为后缀表达式	 * @param inOrderList	 * @return	 */	public ArrayList
      
        getPostOrder(ArrayList
       
         inOrderList){				ArrayList
        
          result = new ArrayList
         
          (); Stack
          
            stack = new Stack
           
            (); for (int i = 0; i < inOrderList.size(); i++) { if(Character.isDigit(inOrderList.get(i).charAt(0))){ result.add(inOrderList.get(i)); }else{ switch (inOrderList.get(i).charAt(0)) { case '(': stack.push(inOrderList.get(i)); break; case ')': while (!stack.peek().equals("(")) { result.add(stack.pop()); } stack.pop(); break; default: while (!stack.isEmpty() && compare(stack.peek(), inOrderList.get(i))){ result.add(stack.pop()); } stack.push(inOrderList.get(i)); break; } } } while(!stack.isEmpty()){ result.add(stack.pop()); } return result; } /** * 计算后缀表达式 * @param postOrder * @return */ public Integer calculate(ArrayList
            
              postOrder){ Stack stack = new Stack(); for (int i = 0; i < postOrder.size(); i++) { if(Character.isDigit(postOrder.get(i).charAt(0))){ stack.push(Integer.parseInt(postOrder.get(i))); }else{ Integer back = (Integer)stack.pop(); Integer front = (Integer)stack.pop(); Integer res = 0; switch (postOrder.get(i).charAt(0)) { case '+': res = front + back; break; case '-': res = front - back; break; case '*': res = front * back; break; case '/': res = front / back; break; } stack.push(res); } } return (Integer)stack.pop(); } /** * 比较运算符等级 * @param peek * @param cur * @return */ public static boolean compare(String peek, String cur){ if("*".equals(peek) && ("/".equals(cur) || "*".equals(cur) ||"+".equals(cur) ||"-".equals(cur))){ return true; }else if("/".equals(peek) && ("/".equals(cur) || "*".equals(cur) ||"+".equals(cur) ||"-".equals(cur))){ return true; }else if("+".equals(peek) && ("+".equals(cur) || "-".equals(cur))){ return true; }else if("-".equals(peek) && ("+".equals(cur) || "-".equals(cur))){ return true; } return false; } public static void main(String[] args) { Calculate calculate = new Calculate(); String s = "12+(23*3-56+7)*(2+90)/2"; ArrayList result = calculate.getStringList(s); //String转换为List result = calculate.getPostOrder(result); //中缀变后缀 int i = calculate.calculate(result); //计算 System.out.println(i); } }