Scratch

package org.thegt.dnsauce.io;
import java.io.*;
import java.util.Scanner;
import org.thegt.dnsauce.*;

@SuppressWarnings("resource")
public class DNSIO {
    private static File hostsFile;
    private static FileInputStream hostsInput;
    private static FileOutputStream hostsOutput;
    static {
        try {
            hostsFile = new File("C:\\Windows\\System32\\drivers\\etc\\hosts");
            hostsInput = new FileInputStream(hostsFile);
            hostsOutput = new FileOutputStream(hostsFile);
            writeExisting();
        }
        catch (IOException e) {
            try {
                hostsFile = new File("/etc/hosts");
                hostsInput = new FileInputStream(hostsFile);
                hostsOutput = new FileOutputStream(hostsFile);
                writeExisting();
            }
            catch (IOException ex) {
                System.err.println("Hosts file not found.");
                System.exit(1);
            }
        }
    }
    
    public static void add (DNSEntry entry) throws IOException {
        Scanner s = new Scanner(hostsInput);
        s.useDelimiter("\\A");
        String hostsFileContents = s.hasNext() ? s.next() : "";
        if (!hostsFileContents.contains(entry.toString()) && !entry.getHost().trim().toLowerCase().equals("localhost")) {
            new PrintStream(hostsOutput).println(entry.toString());
        }
    }
    
    public static void add (DNSEntry[] entries) throws IOException {
        for (DNSEntry entry : entries) {
            add(entry);
        }
    }
    
    public static void remove (DNSEntry entry) throws IOException {
        Scanner s = new Scanner(hostsInput);
        String newHostsFile = "";
        while (s.hasNextLine() && !entry.getHost().trim().toLowerCase().equals("localhost")) {
            String line = s.nextLine();
            if (line != entry.toString()) {
                newHostsFile += line+ "\n";
            }
        }
        FileOutputStream eraser = new FileOutputStream(hostsFile);
        eraser.write(new String().getBytes());
        eraser.close();
        hostsOutput.write(newHostsFile.getBytes());

    }
    
    public static void remove (DNSEntry[] entries) throws IOException {
        for (DNSEntry entry : entries) {
            remove(entry);
        }
    }
    
    public static void clear () throws IOException {
        Scanner s = new Scanner(hostsInput);
        while (s.hasNextLine()) {
            String line = s.nextLine();
            if (!line.contains("#")) {
                remove(new DNSEntry(line));
            }
        }
    }
    
    public static void write(DNSEntry[] entries) throws IOException {
        clear();
        add(entries);
    }
    
    private static void writeExisting () throws IOException {
        Scanner s = new Scanner(hostsInput);
        s.useDelimiter("\\A");
        String existing = s.hasNext() ? s.next() : "";
        byte[] data = existing.getBytes();
        if (existing.length() < 1) {
            System.out.println("WARNING: Hosts file is empty!");
        }
        hostsOutput.write(data);
    }
    
}