import java.util.ArrayList; import java.util.List; import java.util.Scanner; import java.util.regex.Pattern; public class Main { private static String pattern = "^-?[0-9]+"; public static void main(String[] args) { ArrayList<Integer> inputs = new ArrayList<Integer>(); Scanner in = new Scanner(System.in); String line = in.nextLine(); if (line != null && !line.isEmpty()) { int res = resolve(line.trim()); System.out.println(String.valueOf(res)); } } // write your code here public static int resolve(String expr) { int[] stack = new int[16]; int top = -1; String[] datas = expr.split(" "); for (int i = 0; i < datas.length; i++) { if (Pattern.matches(pattern, datas[i])) { if (top == 15) { return -2; } top++; stack[top] = Integer.parseInt(datas[i]); } else { switch (datas[i]) { case "^": if (top == -1) { return -1; } stack[top]++; break; case "+": if (top < 1) { return -1; } int a = stack[top]; top--; stack[top] += a; break; case "*": if (top < 1) { return -1; } int b = stack[top]; top--; stack[top] *= b; break; } } } if (top < 0) { return -1; } return stack[top]; } } 我这个AC了，字符串匹配的没AC，求大神代码