你的太复杂了吧，看看我的 import java.util.*; public class Solution { public String solve (String s, String t) { if(s==null||"".equals(s))return t; if(t==null||"".equals(t))return s; int i=s.length()-1,j=t.length()-1; StringBuilder ans=new StringBuilder(); int c=0; while(i>=0||j>=0){ int c1=(i>=0?s.charAt(i)-'0':0); int c2=(j>=0?t.charAt(j)-'0':0); ans.append((c+c1+c2)%10); c=(c1+c2+c)/10; i--; j--; } if(c!=0) ans.append(c); ans.reverse(); return ans.toString(); } }