[CC150][1.8] 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 (i e , “waterbottle” is a rotation of “erbottlewat”)

isRotation.java

public class isRotation {
	
	public static boolean isRotate(String s1, String s2) {
		if (s1.length() != s2.length()) return false;
		return isSubstring(s2, s1.concat(s1));		
	}
	

	public static boolean isSubstring(String s1, String s2) {
		int l2 = s2.length();
		int l1 = s1.length();
		if (l1 > l2) return false;
		if (l1 == 0 && l2 == 0) return true;
		int k, j;
		for (int i = 0; i < l2; i++ ) {
			k = i;
			j = 0;
			while (s2.charAt(k++) == s1.charAt(j++)) {
				if (j == l1) return true;
			}
		}
		return false;
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		String a = "erbottlewat";
		String b = "water";
		if (isRotation.isRotate(a, b))
			System.out.println("Yes");
		else
			System.out.println("No");		
	}

}