/* Given a string and a non-empty substring sub, compute recursively if at * least n copies of sub appear in the string somewhere, possibly with * overlapping. N will be non-negative. */ public boolean strCopies(String str, String sub, int n) { if(n == 0) return true; if(str.length() < sub.length()) return false; if(str.substring(0, sub.length()).equals(sub)) return strCopies(str.substring(1), sub, n-1); return strCopies(str.substring(1), sub, n); }