code: package zemberek.langid.model;
  
  import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.DataInputStream;
  import java.io.DataOutputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Serializable;
  import java.util.List;
  import zemberek.core.collections.Histogram;
  
  /**
   * This model holds the counts of char ngrams.
   */
  public class CharNgramCountModel extends BaseCharNgramModel implements Serializable {
  
    private static final long serialVersionUID = 0xBEEFCAFEABCDL;
    private Histogram<String>[] gramCounts;
  
    public CharNgramCountModel(String modelId, int order) {
      super(modelId, order);
      gramCounts = new Histogram[order + 1];
      for (int i = 0; i < gramCounts.length; i++) {
        gramCounts[i] = new Histogram<>();
      }
    }
  
    private CharNgramCountModel(String id, int order, Histogram<String>[] gramCounts) {
      super(id, order);
      this.gramCounts = gramCounts;
    }
  
    /**
     * Loads data from the custom serialized file and generates a CharNgramCountModel from it.
     *
     * @param f file to load data.
     * @return a CharNgramCountModel generated from file.
     */
    public static CharNgramCountModel load(File f) throws IOException {
      return load(new FileInputStream(f));
    }
  
    /**
     * Loads data from the custom serialized file and generates a CharNgramCountModel from it.
     *
     * @param is InputStream to load data.
     * @return a CharNgramCountModel generated from file.
     */
    public static CharNgramCountModel load(InputStream is) throws IOException {
      try (DataInputStream dis = new DataInputStream(new BufferedInputStream(is))) {
        int order = dis.readInt();
        String modelId = dis.readUTF();
        Histogram<String>[] gramCounts = new Histogram[order + 1];
        for (int j = 1; j <= order; j++) {
          int size = dis.readInt();
          Histogram<String> countSet = new Histogram<>(size * 2);
          for (int i = 0; i < size; i++) {
            String key = dis.readUTF();
            countSet.add(key, dis.readInt());
          }
          gramCounts[j] = countSet;
  
        }
        return new CharNgramCountModel(modelId, order, gramCounts);
      }
    }
  
    /**
     * A custom serializer. Big-endian format is like this: int32 order Utf id int32 keyCount utf key
     * int32 count ... int32 keyCount utf key int32 count ...
     *
     * @param f file to serialize.
     */
    public void save(File f) throws IOException {
      try (DataOutputStream dos = new DataOutputStream(
          new BufferedOutputStream(new FileOutputStream(f)))) {
        dos.writeInt(order);
        dos.writeUTF(id);
        for (int i = 1; i < gramCounts.length; i++) {
          dos.writeInt(gramCounts[i].size());
          for (String key : gramCounts[i]) {
            dos.writeUTF(key);
            dos.writeInt(gramCounts[i].getCount(key));
          }
        }
      }
    }
  
  
    public void addGrams(String seq) {
      for (int i = 1; i <= order; ++i) {
        List<String> grams = this.getGram(seq, i);
        for (String gram : grams) {
          gramCounts[i].add(gram);
        }
      }
    }
  
    public void applyCutOffs(int[] cutOffs) {
      if (cutOffs == null) {
        return;
      }
      if (cutOffs.length > order) {
        throw new IllegalArgumentException(
            "Cannot apply cutoff values. Cutoff array length " + cutOffs.length
                + " is larger than the order of the model " + order);
      }
      if (cutOffs.length > 0) {
        for (int i = 0; i < cutOffs.length; i++) {
          int o = i + 1;
          System.out.println(o + " gram Count Before cut off: " + keyCount(o));
          removeSmaller(o, cutOffs[i] + 1);
          System.out.println(o + " gram Count After cut off: " + keyCount(o));
        }
      }
    }
  
    public void merge(CharNgramCountModel otherModel) {
      if (otherModel.order != order) {
        throw new IllegalArgumentException(
            "Model orders does not match. Order of this model is" + order +
                " but merged model order is " + otherModel.order);
      }
      for (int i = 1; i < gramCounts.length; i++) {
        gramCounts[i].add(otherModel.gramCounts[i]);
      }
    }
  
    public int getCount(int order, String key) {
      return gramCounts[order].getCount(key);
    }
  
    public void add(int order, String key) {
      gramCounts[order].add(key);
    }
  
    public int keyCount(int order) {
      return gramCounts[order].size();
    }
  
    public boolean containsKey(int order, String key) {
      return gramCounts[order].contains(key);
    }
  
    public int removeSmaller(int order, int size) {
      return gramCounts[order].removeSmaller(size);
    }
  
    public int totalCount(int order) {
      return (int) gramCounts[order].totalCount();
    }
  
    public Iterable<String> getKeyIterator(int order) {
      return gramCounts[order];
    }
  
    public Iterable<String> getSortedKeyIterator(int order) {
      return gramCounts[order].getSortedList();
    }
  
    public void dumpGrams(int order) {
      for (String s : getSortedKeyIterator(order)) {
        System.out.println(s + " : " + getCount(order, s));
      }
    }
  }
  