京东java笔试，删除一个或者多个字符串后回文串的数目问题

	import java.util.ArrayList;
import java.util.Scanner;



	public class Main {


static int count = 0;
public boolean isFalg(String s){
    int len = s.length();
    int left = 0;
    int right = len-1;
    while(left <= right){
        if(s.charAt(left) != s.charAt(right)){
            return false;
        }
        right--;
        left++;
    }

    return true;
}

public void traceBack(String s,ArrayList<Character> list){
    int len = s.length();
    if(len == 0){
        return;
    }
    //System.out.println(list.toString());
    for(int i=0;i<s.length();i++){
        //System.out.println("index:"+i+"char:"+s.charAt(i));
        list.add(s.charAt(i));
        StringBuilder builder = new StringBuilder();
        for(int j=0;j<list.size();j++){
            builder.append(list.get(j));
        }
        if(isFalg(builder.toString())){
            System.out.println(builder.toString());
            count++;
        }
        System.out.println("index:"+i);
        if(i+1 < s.length())
        traceBack(s.substring(i+1),list);
        list.remove(list.size()-1);
    }
}

public static void main(String args[]){
    Scanner sc = new Scanner(System.in);
    String s = sc.nextLine();
    int len = s.length();
    ArrayList<Character> list = new ArrayList<Character>();
    Main main = new Main();

    main.traceBack(s, list);
    String ss = "ABA";
    System.out.println(main.isFalg(ss));
    System.out.println(count);
}

	}