java实现中缀表达式转后缀表达式

 package postfix;

 import java.util.Stack;

 /**
  *
  * @author DELL 将中缀表达式转化为后缀表达式
  */

 public class Expression {
     private StringBuffer iExp; // 存储中缀表达式
     private Stack stack;
     private StringBuffer pExp; // 存储后缀表达式

     public Expression(String s) {
         iExp = new StringBuffer(s);
         stack = new Stack();
         pExp = new StringBuffer();
     }

     public String toPostfix() throws Exception {
         while (iExp.length() != 0) {
             char c = iExp.charAt(0);
             iExp.deleteCharAt(0);
             switch (c) {
             case '0':
             case '1':
             case '2':
             case '3':
             case '4':
             case '5':
             case '6':
             case '7':
             case '8':
             case '9':
                 pExp.append(c);
                 break;
             case '(':
                 stack.push(c);
                 break;
             case ')':
                 while (stack.peek() != (Object) '(') {
                     pExp.append(stack.pop());
                 }
                 stack.pop();
                 break;
             case '+':
             case '-':
                 while (!stack.isEmpty() && stack.peek() != (Object) '(') {
                     pExp.append(stack.pop());
                 }
                 stack.push(c);

                 break;
             case '*':
             case '/':
                 while (!stack.isEmpty() && stack.peek() != (Object) '(' && stack.peek() != (Object) '+'
                         && stack.peek() != (Object) '-') {
                     pExp.append(stack.pop());
                 }
                 stack.push(c);
                 break;
             case '^':
                 stack.push('^');
                 break;
             default:
                 System.out.println("出现错误字符"+c);
                 break;
             }

         }
         while (!stack.isEmpty()) {
             pExp.append(stack.pop());
         }
         return pExp.toString();
     }

 }

撰写时间：2017-08-13 16:50:11

修改时间：