递归验证回文

package 递归;
import java.util.Scanner;

public class Calculate{
        
    System.out.println("请输入字符串"); 
    static String str=new String();
    static boolean fase;
    
    Scanner in=new Scanner(System.in);
    str=in.nextLine();
    public static void main(String[] args) {
    f(0,str.length()-1);
    if(f(0,str.length()-1))
        System.out.println("是回文");
    else
        System.out.println("不是回文");
    }

  public static boolean f(int i,int j)
  {
      if((j-i==0)||(j-i==1))
      { fase=true; }
      else
       {  if(str.charAt(i)==str.charAt(j))
            f(i++,j--);
          else
          fase=false;
      }
  }
 
}