– Create 1 class array initialization (class InitArray)
– Create 1 Import Export array class inherits from the class file to initialize the array (class IOArray extends InitArray)
– Create 1 sorted array class inheriting class array initialization (class SortArray extends InitArray)
– Class arrays (Array) contains the main function() program execution
Here is the code:

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;
class InitArray
{
	int [] Element;
}
class IOArray extends InitArray
{
	void input_file() throws FileNotFoundException
	{
		FileInputStream fi = new FileInputStream("input.txt");
		Scanner inp = new Scanner(fi,"UTF-8");
		String temp = inp.nextLine(); //doc dong mang trong file
		inp.close();
		String [] item = temp.split(" "); //tach chuoi thanh cac phan tu chuoi
		Element = new int[item.length];
		for(int i=0; i<item.length; i++) //doi kiem string sang int cua cac phan tu
			Element[i] = Integer.parseInt(item[i]);
	}
	void output_file() throws IOException
	{
		FileOutputStream fo = new FileOutputStream("output.txt");
		PrintWriter out = new PrintWriter(fo);
		for (int i=0; i<Element.length; i++)
			out.printf("%-5d",Element[i]);
		out.close();
	}
}

class SortArray extends InitArray
{
	public void sort(IOArray A) //phuong thuc sap xep
	{
		Arrays.sort(A.Element);
	}
}

class Array
{
	public static void main(String[] args) throws IOException
	{
		IOArray Arr = new IOArray();
		Arr.input_file(); //nhap tu file
		SortArray SArr = new SortArray();
		SArr.sort(Arr); //sap xep
		Arr.output_file(); //xuat ra file
		System.out.println("nSucces ! Open file output.txt to view");
	}
}