public static void main(String[] args) {

String s1 = "11";

String s2 = "2119";

String s3 = "116";

decodeNumber(s1);

decodeNumber(s2);

decodeNumber(s3);

}

public static void decodeNumber(String s) {

int len = s.length();

if (len == 0) {

System.out.println("empty string");

return;

}

for (int i = 0; i < len; i++) {

if (!((s.charAt(i) - '0') <= 9) && !(('9' - s.charAt(i)) >= 0)) {

System.out.println(s + " is not number.");

return;

}

}

int[] ways = new int[len];

ways[0] = (s.charAt(0) == '0') ? 0 : 1;

for (int i = 1; i < len; i++) {

char p = s.charAt(i - 1);

char c = s.charAt(i);

if (p !='0' && ways[i - 1] == 0)

ways[i] = 1;

if ( ways[i-1] != 0) {

ways[i] = ways[i-1];

}

if (p == '1' || (p == '2' && c <= '6')) {

if(i>=2)

ways[i] = ways[i - 2] + ways[i];

else

ways[i] = ways[i-1] + ways[i];

}

}

System.out.println(s + ":" + ways[len - 1]);

}