Someone

import java.io.*;
public class FreeMem {
    public int FreeMem() 
    {
        try
        {
            Process p=Runtime.getRuntime().exec ("free");
            InputStream is = p.getInputStream();
            BufferedReader br = new BufferedReader (new InputStreamReader (is));
            String aux = br.readLine();
	    aux = br.readLine();
            System.out.println (aux);
	    String free_mem = aux.substring(36,40);
	    return Integer.valueOf(free_mem);
        } 
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        new FreeMem();
    }
    
}