File question (sorta)

String row = "1 2 3 4 5";

// a) use String.split, it returns an array (that you can loop over - read split docs)
for (String part : row.split("\\s"))
    // find the max here
    System.out.println(Integer.parseInt(part));

// b) pattern-matcher
Matcher m = Pattern.compile("[+-]{0,1}\\d+").matcher(row); // or just \\w+ as regex for finding entire words
while (m.find()) {
    System.out.println(m.group());
}

// c)  or make it more complicated and use substring (just to show that there are more possibilities)
// adding the delimiter to the end to make things a little bit easier (or check for end of the string reached)
row += " ";
int
        from = 0,
        to = 0;

while (from < row.length()) { // as long es the end isn't reached
    while (row.charAt(++to) != ' ') ; // find the next delimiter, loop ends in the same line
    System.out.println(row.substring(from, to)); // and output from-to, in your case parse and find max here
    from = to + 1;
}

// d) use a Stream (using split again, but this time from several lines, again, just to show it's possible)
String[] fileContent = new String[] {
        "2 4 1 10",
        "3 5 -2 8 13 7",
        "12 -1 9"
};

System.out.println("the max is: " +
        Arrays.stream(fileContent)
                .flatMap(line -> Stream.of(line.split("\\s")))
                .mapToInt(Integer::parseInt)
                .max()
                .getAsInt()
);

// e) ....