How can I achieve a repeated string match in programming?

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给定两个字符串A和B，找出A需要重复的最小次数，使得B成为它的子串。如果不存在这样的解，则返回-1。例如，如果A=abcd和B=cdabcdab，则返回3，因为通过重复A三次，可以得到abcdabcdabcd，B是它的子串。

Given two strings A and B, find the minimum number of times A has to be repeated such that B is a substring of it. If no such solution, return -1.

For example, with A = “abcd” and B = “cdabcdab”.

Return 3, because by repeating A three times (“abcdabcdabcd”), B is a substring of it; and B is not a substring of A repeated two times (“abcdabcd”).

Note:
The length of A and B will be between 1 and 10000.

class Solution {
public int repeatedStringMatch(String A, String B) {
String t = A ;
for(int i = 1 ; i <= B.length()/A.length()+2 ; i++){
if (t.indexOf(B) != -1)
return i ;
else
t += A