用递归判断字符串是否为回文

import java.util.Scanner;

public class Huiwen {
    static char []a=new char[1000];
    static String str;
    static int f=0;
    static int n=0;
    static Scanner sc=new Scanner(System.in);
    public static void main(String[] args) {
        str=sc.nextLine();
        a=str.toCharArray();
        huiWen(a,n);
        if(f==0) {
            System.out.println(str+" : "+"不是回文序列");
        }
        else {
            System.out.println(str+" : "+"是回文序列");
        }
    }
    public static void huiWen(char[] a,int n) {
        if(a.length==1||a.length==0) {
            f=1;
            return ;
        }
        if(a.length-2*n-1==1) {
            f=1;
            return ;
        }
        if(a.length-2*n-1==2) {
            if(a[n]==a[a.length-n-1]) {
                f=1;
                return ;
            }
            else {
                f=0;
                return ;
            }
        }
        
        if(a[n]==a[a.length-n-1]) {
            n=n+1;
            huiWen(a,n);
            
        }
        else {
            f=0;
            return ;
        }
        
    }

}