Assume you have a method isSubstring which checks if one word is a
substring of another. Given two strings, s1 and s2, write code to check if s2 is
a rotation of s1 using only one call to isSubstring (e.g.,"waterbottle"is a rotation
of "erbottlewat").
1 public static boolean isRotation(String s1, String s2) { 2 if(s1 == null || s2 == null) return false; 3 if(s1.length() != s2.length()) return false; 4 5 String s3 = s1 + s1; 6 return isSubstring(s3, s2); 7 }
原文：http://www.cnblogs.com/superbo/p/4112790.html