java 判断一串字符串 java判断字符串个数

import java.util.Scanner;

public class Main01 {

    static int counter = 0;
    public static int countStr(String str1, String str2) {
        if (str1.indexOf(str2) == -1) {
            return 0;
        } else if (str1.indexOf(str2) != -1) {
            counter++;
            countStr(str1.substring(str1.indexOf(str2) +
                    str2.length()), str2);
            return counter;
        }
        return 0;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.nextLine();
        System.out.println(countStr(s,"AB"));

    }
        }