public class BinString { public BinString() {} public String convert(String s) { return binarise(sum(s)); } public int sum(String s) { if (s=="") return 0; if (s.length ()==1) return ((int)(s.charAt(0))); return ((int)(s.charAt(0))) + sum(s.substring(1)); } public String binarise(int x) { if (x==0) return ""; if (x%2==1) return "1" + binarise(x/2); return "0"+binarise(x/2); } }