两个字符串A,B，求B在A中首次出现的位置，如果B不在A中返回-1.

package paixu;
import java.util.*;

/**
 * Created by Administrator on 2017/9/17.
 */
public class PIpei {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while(in.hasNext()){
            String str1=in.nextLine();
            String str2 =in.nextLine();
            pipei(str1,str2);
        }
    }
    public static int pipei(String str1,String str2) {
        int len1 = str1.length();
        int len2 = str2.length();
        int i = 0;
        int j = 0;
        while (i < len1 && j < len2) {
            if (str1.charAt(i) == str2.charAt(j)) {
                i++;
                j++;
            } else {
                i = i - j + 1;
                j = 0;
            }
            if (j == len2) {
              System.out.println(i - j + 1);
            }
            }
        return -1;
        }

    }