import java.io.*;
import java.util.HashMap;
import java.util.Map;


/**
 * Created by user on 3/30/2017.
 */
public class test {

    private static String filePath = "test7.txt";
    protected HashMap<String, String> map = new HashMap<String, String>();



    public static void main(String[] args) throws IOException{
        new test().clearHosts();

        new test().addHost("google.com", "174.73.95.94");

        new test().deleteHost("google.com");


    }

    private void readHosts() throws IOException{
        String line;
        BufferedReader reader = new BufferedReader((new FileReader(filePath)));
        while ((line = reader.readLine()) != null) {
            String[] parts = line.trim().split(" ");
            if (!line.startsWith("#")) {
                String value = parts[0];
                String key = parts[1];
                map.put(key, value);
            }
        }
        reader.close();
    }

    private void writeHosts(HashMap<String, String> map) throws IOException {
        FileWriter writer = new FileWriter("test7.txt");
        for(Map.Entry<String, String> entry : map.entrySet()) {
            writer.write(entry.getValue() + " " + entry.getKey() + "\n");
        }
        writer.close();

    }

    public void addHost(String host, String ip) throws IOException{
        readHosts();
        if (!map.containsKey(host)) {
            map.put(host, ip);
        }
        writeHosts(map);
    }

    public void deleteHost(String host) throws IOException{
        readHosts();
        if (map.containsKey(host)) {
            map.remove("google.com");
        }
        writeHosts(map);
    }

    public void createHosts(){

    }

    public void clearHosts() throws IOException{
        HashMap<String, String> map1 = new HashMap<String, String>();
        map1.put("localhost", "127.0.0.1");
        map1.put("::1", "localhost");
        writeHosts(map1);
    }
}