Check if s2 is a rotation of s1 using only one call to isSubstring. CC150 - Arrays and Strings

IsRotation.java

package CC150.ArraysAndString;

/**
 * Check if s2 is a rotation of s1 using only one call to isSubstring
 * eg: "waterbottle" is a rotation of "erbottlewat" 
 *
 */
public class IsRotation {

	public boolean isRotation2(String s1, String s2) {
		// error checking
		if ((s1.length() != s2.length()) && (s1.length() >0)) {
			return false;
		}
		
		String newStr =  s1.concat(s1);  // String newStr = s1 + s1; also works
		return isSubstring(newStr, s2);
	}

	private boolean isSubstring(String newStr, String s2) {
		// TODO Auto-generated method stub
		return false;
	}
}