I suggest you avoid storing all the lines. Instead you can copy the data as you read it. You don't actually need to parse each line after the first, you just need to copy the rest of the data.
try(BufferedReader in = new BufferedReader(new FileReader(file_live);
BufferedWriter out = new BufferedWriter(new FileWriter(file_live+".tmp"))) {
// skip the first line
in.readLine();
char[] buffer = new char[8*1024];
for(int len; (len = in.read(buffer)) > 0;)
out.write(buffer, 0, len);
}
new File(file_live).delete();
new File(file_live+".tmp").renameTo(new File(file_live));
BTW: consuming one line at a time this way is very expensive, esp if the file is large. If you can I would suggest not re-writing the file at all and instead record separately which line you were up to.