Valid Number

 1 public boolean isNumber(String s) {
 2     int i = 0;
 3     int n = s.length();
 4 
 5     // 略过s前面的空格
 6     while(i < n && Character.isWhitespace(s.charAt(i))) {
 7         i++;
 8     }
 9 
10     boolean isNumeric = false;
11 
12     while(i < n && Character.isDigit(s.charAt(i))) {
13         i++;
14         isNumeric = true;
15     }
16 
17     if(i < n && s.charAt(i) == ‘.‘) {
18         i++;
19         while(i < n && Character.isDigit(s.charAt(i))) {
20             i++;
21             isNumeric = true;
22         }
23     }
24 
25     // 略过s后面的空格
26     while(i < n && Character.isWhitespace(s.charAt(i))) {
27         i++;
28     }
29 
30     return isNumerics && i == n;
31 }