java算法回文体的判断

import java.util.*;

import java.math.BigInteger;

import java.util.Scanner;

public class Test{    

         static Scanner a=new Scanner(System.in);

         static char str[] = new char[99];

         static int l=0;

         public static void main(String[] args) {

                  System.out.println("请输入字符串:");

                  String b = a.next();

                  for(int i=0;i<b.length();i++) {//字符数组

                          str[l] = b.charAt(i);

                          l++;

                  }

                  boolean hw = Huiwen(str, 0, l-1,l);

                  if(hw) {

                          System.out.println("是回文");

                  }

                  else

                  {

                          System.out.println("不是是回文");

                  }

         }

         public static boolean Huiwen(char a[],int first,int end,int length){

                  if(length == 1 || length == 0)

                          return true;

                  if (a[first] != a[end] || first >= end) {//第一个字符与最后一个字符比较

                          return false;

                  }

                  return Huiwen(a, first + 1, end -1,length -2);//两边靠拢

         }

         }