Partition a list

Partition.java

package sj.util;

import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import org.springframework.lang.NonNull;

/**
 * The type Partition.
 *
 * @param <T> the type parameter
 */
public final class Partition<T> extends AbstractList<List<T>> {

  /** The List. */
  private final List<T> list;

  /** The Chunk size. */
  private final int chunkSize;

  /**
   * Instantiates a new Partition.
   *
   * @param list the list
   * @param chunkSize the chunk size
   */
  Partition(@NonNull Collection<T> list, int chunkSize) {
    this.list = new ArrayList<>(list);
    this.chunkSize = chunkSize;
  }

  /**
   * Of size partition.
   *
   * @param <T> the type parameter
   * @param list the list
   * @param chunkSize the chunk size
   * @return the partition
   */
  @NonNull
  public static <T> Partition<T> ofSize(@NonNull Collection<T> list, int chunkSize) {
    return new Partition<>(list, chunkSize);
  }

  /**
   * Get list.
   *
   * @param index the index
   * @return the list
   */
  @Override
  @NonNull
  public List<T> get(int index) {
    int start = index * chunkSize;
    int end = Math.min(start + chunkSize, list.size());

    if (start > end) {
      throw new IndexOutOfBoundsException(
          String.format("Index %d  is out of the list range <0,%d>", index, size() - 1));
    }
    return new ArrayList<>(list.subList(start, end));
  }

  /**
   * Size int.
   *
   * @return the int
   */
  @Override
  public int size() {
    return (int) Math.ceil((double) list.size() / (double) chunkSize);
  }

  /**
   * To string string.
   *
   * @return the string
   */
  @Override
  public String toString() {
    return "Partition{" + "list=" + list + ", chunkSize=" + chunkSize + "} " + super.toString();
  }
}