I think it is working as requested. So, what's wrong?
package com.codegym.task.task07.task0721;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
/*
Min and max in arrays
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int[] numbers = new int[20];
int maximum = 0;
int minimum = 0;
for (int index = 0; index < numbers.length; index ++) {
int number = Integer.parseInt(reader.readLine());
numbers[index] = number;
maximum = Math.max(maximum, numbers[index]);
minimum = index == 0 ? numbers[index] : Math.min(minimum, numbers[index]);
}
System.out.print(maximum + " " + minimum);
}
}