Parsing numbers

Integer.parseInt("42") turns text into an int, Double.parseDouble("1.5") into a double, and String.valueOf(42) or "" + 42 go the other way. Text that is not a number makes parseInt throw a NumberFormatException, which ends the program unless something catches it.

Catching is try { ... } catch (NumberFormatException e) { ... }: the code in try runs, and if it throws that exception, the catch block runs instead of the program stopping. The exceptions module covers this properly; for now it is the tool that makes parsing user input safe.

int n;
try {
    n = Integer.parseInt(text.trim());
} catch (NumberFormatException e) {
    n = 0;
}

Your task

Write static int safeParse(String text, int fallback) returning the number in the text (surrounding spaces allowed) or the fallback when it is not a whole number, static double average(String[] numbers) returning the mean of the texts that parse as doubles (ignoring the ones that do not; 0 when none do), and static String percent(int part, int whole) returning the whole-number percentage with a percent sign (percent(1, 3) is "33%").

public class Main {
    static int safeParse(String text, int fallback) {
        try {
            return Integer.parseInt(text.trim());
        } catch (NumberFormatException e) {
            return fallback;
        }
    }

    static double average(String[] numbers) {
        double sum = 0;
        int count = 0;
        for (String n : numbers) {
            try {
                sum += Double.parseDouble(n);
                count++;
            } catch (NumberFormatException e) {
                // skip it
            }
        }
        return count == 0 ? 0 : sum / count;
    }

    static String percent(int part, int whole) {
        return 100 * part / whole + "%";
    }

    public static void main(String[] args) {
        System.out.println(safeParse(" 42 ", 0) + " " + safeParse("x", 7) + " " + percent(1, 3));
    }
}