code: import java.io.*;
  import java.util.*;
  import java.util.regex.*;
  
  public class UpdateConfig {
  
      public static void main(String[] args) {
          if (args[0] == null) {
              System.out.println("filename required");
  
          } else if (readConfig(args[0])) {
              enableOption("seedsremoved");
              disableOption("needspeeling");
              setOption("numberofbananas", "1024");
              addOption("numberofstrawberries", "62000");
              store();
          }
      }
  
      private enum EntryType {
          EMPTY, ENABLED, DISABLED, COMMENT
      }
  
      private static class Entry {
          EntryType type;
          String name, value;
  
          Entry(EntryType t, String n, String v) {
              type = t;
              name = n;
              value = v;
          }
      }
  
      private static Map<String, Entry> entries = new LinkedHashMap<>();
      private static String path;
  
      private static boolean readConfig(String p) {
          path = p;
  
          File f = new File(path);
          if (!f.exists() || f.isDirectory())
              return false;
  
          String regexString = "^(;*)\\s*([A-Za-z0-9]+)\\s*([A-Za-z0-9]*)";
          Pattern regex = Pattern.compile(regexString);
  
          try (Scanner sc = new Scanner(new FileReader(f))){
              int emptyLines = 0;
              String line;
              while (sc.hasNext()) {
                  line = sc.nextLine().trim();
  
                  if (line.isEmpty()) {
                      addOption("" + emptyLines++, null, EntryType.EMPTY);
  
                  } else if (line.charAt(0) == '#') {
                      entries.put(line, new Entry(EntryType.COMMENT, line, null));
  
                  } else {
                      line = line.replaceAll("[^a-zA-Z0-9\\x20;]", "");
                      Matcher m = regex.matcher(line);
  
                      if (m.find() && !m.group(2).isEmpty()) {
  
                          EntryType t = EntryType.ENABLED;
                          if (!m.group(1).isEmpty())
                              t = EntryType.DISABLED;
  
                          addOption(m.group(2), m.group(3), t);
                      }
                  }
              }
          } catch (IOException e) {
              System.out.println(e);
          }
          return true;
      }
  
      private static void addOption(String name, String value) {
          addOption(name, value, EntryType.ENABLED);
      }
  
      private static void addOption(String name, String value, EntryType t) {
          name = name.toUpperCase();
          entries.put(name, new Entry(t, name, value));
      }
  
      private static void enableOption(String name) {
          Entry e = entries.get(name.toUpperCase());
          if (e != null)
              e.type = EntryType.ENABLED;
      }
  
      private static void disableOption(String name) {
          Entry e = entries.get(name.toUpperCase());
          if (e != null)
              e.type = EntryType.DISABLED;
      }
  
      private static void setOption(String name, String value) {
          Entry e = entries.get(name.toUpperCase());
          if (e != null)
              e.value = value;
      }
  
      private static void store() {
          try (PrintWriter pw = new PrintWriter(path)) {
              for (Entry e : entries.values()) {
                  switch (e.type) {
                      case EMPTY:
                          pw.println();
                          break;
                      case ENABLED:
                          pw.format("%s %s%n", e.name, e.value);
                          break;
                      case DISABLED:
                          pw.format("; %s %s%n", e.name, e.value);
                          break;
                      case COMMENT:
                          pw.println(e.name);
                          break;
                      default:
                          break;
                  }
              }
              if (pw.checkError()) {
                  throw new IOException("writing to file failed");
              }
          } catch (IOException e) {
              System.out.println(e);
          }
      }
  }
  