Valid Number

Validate if a given string is numeric.
Some examples:
"0" => true
" 0.1 " => true
"abc" => false
"1 a" => false
"2e10" => true

Note: It is intended for the problem statement to be ambiguous. You should 

gather all requirements up front before implementing one.

题目是判断一个字符串是否是一个数字，默认所有字符串是小写的，‘1.’这样的

字符是数字，指数e后面可以有正负号，但数字必须是整数，否则OJ不通过。

public static boolean isNumber(String s) {s=s.trim();int len = s.length();int i = 0, e = len - 1;if(i>e)return false;if(s.charAt(i)=='+'||s.charAt(i)=='-')i++;boolean num=false,doc=false,exp=false;while(i<=e){char c=s.charAt(i);if(Character.isDigit(c))num=true;else if(c=='.'){if(doc||exp)return false;doc=true;}else if(c=='e'){if(exp||num==false)return false;exp=true;num=false;}else if(c=='+'||c=='-'){if(s.charAt(i-1)!='e')return false;}else return false;i++;}return num;}