individual.java

来自「java编程思想(第四版)书中原代码 ,对初学者很有用的东西」· Java 代码 · 共 42 行

//: typeinfo/pets/Individual.java
package typeinfo.pets;

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() {}
  public String toString() {
    return getClass().getSimpleName() +
      (name == null ? "" : " " + name);
  }
  public long id() { return id; }
  public boolean equals(Object o) {
    return o instanceof Individual &&
      id == ((Individual)o).id;
  }
  public int hashCode() {
    int result = 17;
    if(name != null)
      result = 37 * result + name.hashCode();
    result = 37 * result + (int)id;
    return result;
  }
  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));
  }
} ///:~