Write a program that takes an integer number and converts it to base-7:

Write a program that converts from a base-7 number to its decimal representation:

edited

Here is the solution for the first part: Write a program that takes an integer number and converts it to base-7:

```import java.util.ArrayList;
import java.util.Scanner;

public class Pr_04_ConvertFromDecimalSystemToBase7 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int number = scanner.nextInt();
ArrayList<Integer> result = new ArrayList<>();

int remainder = 0;
boolean finish = false;

while (!finish) {
if (number == 0) {
finish = true;
} else {
remainder = number % 7;
number = number / 7;
}
remainder = 0;
}
for (int i = result.size()-1; i >=0 ; i--) {
int a = result.get(i);
System.out.print(a);
}
System.out.println();
}
}```

...and for the second part: Convert from base-7 to decimal:

```import java.util.Locale;
import java.util.Scanner;

public class Main {

public static void main(String[] args) {

Scanner console = new Scanner(System.in);
int result = 0;

char[] chars = console.nextLine().toCharArray();

int[] reverse = new int[chars.length];

for (int i = chars.length - 1, j = 0; i >= 0; i--, j++) {

reverse[j] = Integer.parseInt(String.valueOf(chars[i]));
}

for (int i = 0; i < reverse.length; i++) {

int sum = (int) (reverse[i] * Math.pow(7, i));

result += sum;
}
System.out.println(result);
}
}```