DFA(判断是否是数字)

这段代码真是太精密了。

public boolean isNumber(String s) {    s = s.trim();    boolean pointSeen = false;    boolean eSeen = false;    boolean numberSeen = false;    boolean numberAfterE = true;    for(int i=0; i<s.length(); i++) {        if('0' <= s.charAt(i) && s.charAt(i) <= '9') {            numberSeen = true;            numberAfterE = true;        } else if(s.charAt(i) == '.') {            if(eSeen || pointSeen) {                return false;            }            pointSeen = true;        } else if(s.charAt(i) == 'e') {            if(eSeen || !numberSeen) {                return false;            }            numberAfterE = false;            eSeen = true;        } else if(s.charAt(i) == '-' || s.charAt(i) == '+') {            if(i != 0 && s.charAt(i-1) != 'e') {                return false;            }        } else {            return false;        }    }    return numberSeen && numberAfterE;}