OnJava8-Examples/typeinfo/pets/Individual.java

// typeinfo/pets/Individual.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
package typeinfo.pets;
import java.util.*;

public class
Individual implements Comparable<Individual> {
  private static long counter = 0;
  private final long id = counter++;
  private String name;
  public Individual(String name) { this.name = name; }
  // 'name' is optional:
  public Individual() {}
  @Override public String toString() {
    return getClass().getSimpleName() +
      (name == null ? "" : " " + name);
  }
  public long id() { return id; }
  @Override public boolean equals(Object o) {
    return o instanceof Individual &&
      Objects.equals(id, ((Individual)o).id);
  }
  @Override public int hashCode() {
    return Objects.hash(name, id);
  }
  @Override public int compareTo(Individual arg) {
    // Compare by class name first:
    String first = getClass().getSimpleName();
    String argFirst = arg.getClass().getSimpleName();
    int firstCompare = first.compareTo(argFirst);
    if(firstCompare != 0)
      return firstCompare;
    if(name != null && arg.name != null) {
      int secondCompare = name.compareTo(arg.name);
      if(secondCompare != 0)
        return secondCompare;
    }
    return (arg.id < id ? -1 : (arg.id == id ? 0 : 1));
  }
}