请用Java写准波兰变换，使用户输入的中缀表达式，输出后缀表达式

以下是使用Java实现准波兰变换，将中缀表达式转换为后缀表达式的代码：

import java.util.*;

public class QFT {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("请输入中缀表达式：");
        String infix = sc.nextLine();
        String postfix = infixToPostfix(infix);
        System.out.println("后缀表达式为：" + postfix);
    }

    //中缀表达式转后缀表达式
    public static String infixToPostfix(String infix) {
        StringBuilder postfix = new StringBuilder();
        Stack<Character> stack = new Stack<>();

        for (int i = 0; i < infix.length(); i++) {
            char ch = infix.charAt(i);
            if (ch == ' ') {
                continue;
            } else if (Character.isDigit(ch)) {
                postfix.append(ch);
                while (i + 1 < infix.length() && Character.isDigit(infix.charAt(i + 1))) {
                    i++;
                    postfix.append(infix.charAt(i));
                }
                postfix.append(" ");
            } else if (ch == '(') {
                stack.push(ch);
            } else if (ch == ')') {
                while (!stack.isEmpty() && stack.peek() != '(') {
                    postfix.append(stack.pop() + " ");
                }
                stack.pop();
            } else {
                while (!stack.isEmpty() && getPriority(ch) <= getPriority(stack.peek())) {
                    postfix.append(stack.pop() + " ");
                }
                stack.push(ch);
            }
        }

        while (!stack.isEmpty()) {
            postfix.append(stack.pop() + " ");
        }

        return postfix.toString();
    }

    //获取运算符优先级
    public static int getPriority(char ch) {
        if (ch == '+' || ch == '-') {
            return 1;
        } else if (ch == '*' || ch == '/') {
            return 2;
        } else if (ch == '^') {
            return 3;
        } else {
            return 0;
        }
    }
}

使用示例：

输入：`(1+2)*3-4/5`

输出：`12+3*45/-`