public boolean isNumber(String s) {

// Start typing your Java solution below

// DO NOT write main() function

int len = s.length();

boolean hasdot = false;

boolean hase = false;

boolean hasnum = false;

if(len==0) return false;

// get the first non-space charater

int start = 0;

while(start<len){

if(s.charAt(start)==' ')

start++;

else

break;

}

// all spaces

if(start==len) return false;

// get last non-space character

int end = len-1;

while(end>start){

if(s.charAt(end)==' ')

end--;

else

break;

}

// deal with "+" and "-"

if(s.charAt(start)=='+' || s.charAt(start)=='-')

start++;

else if(s.charAt(start)=='e')

return false;

// start validation

for(int i=start; i<=end; i++){

// deal with '.'

if(s.charAt(i)=='.'){

if(hasdot)

return false;

else

hasdot = true;

}

else if(s.charAt(i)=='e'){

if(!hasnum || hase || i==end ||(i==end-1 && (s.charAt(i+1)=='+' || s.charAt(i+1)=='-'))) //different invalid casse: e34, 34ee, 34e+

return false;

else{

if(s.charAt(i+1)=='-' || s.charAt(i+1)=='+')

i++;

hase = true;

hasdot = true; // after "e" we cannot have any "."

}

}

else if(s.charAt(i)>='0' && s.charAt(i)<='9')

hasnum = true;

else

return false;

}

if(hasnum)

return true;

else

return false;

}

}