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：