246. Strobogrammatic Number

 1     public boolean isStrobogrammatic(String num) {
 2         Map<Character, Character> map = new HashMap<Character, Character>();
 3         map.put(‘6‘, ‘9‘);
 4         map.put(‘9‘, ‘6‘);
 5         map.put(‘1‘, ‘1‘);
 6         map.put(‘8‘, ‘8‘);
 7         map.put(‘0‘, ‘0‘);
 8         int walker = 0;
 9         int runner = num.length() - 1;
10         while(walker <= runner) {
11             if(map.containsKey(num.charAt(walker)) && map.get(num.charAt(walker)) == num.charAt(runner)) {
12                 walker++;
13                 runner--;
14             } else {
15                 return false;
16             }
17         }
18         return true;
19     }