자바 Comparable 과 Comparator 의 상세 한 해석 및 차이

**
 * description:          ,     Comparable   ，    
 * <br/>
 * author: shixinzhang
 * <br/>
 * data: 10/5/2016
 */
public class BookBean implements Serializable, Comparable {
  private String name;
  private int count;


  public BookBean(String name, int count) {
    this.name = name;
    this.count = count;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public int getCount() {
    return count;
  }

  public void setCount(int count) {
    this.count = count;
  }

  /**
   *    equals
   * @param o
   * @return
   */
  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof BookBean)) return false;

    BookBean bean = (BookBean) o;

    if (getCount() != bean.getCount()) return false;
    return getName().equals(bean.getName());

  }

  /**
   *    hashCode      
   *              ，    
   *    hashCode        31     ，     ，     
   * @return
   */
  @Override
  public int hashCode() {
    //   String   hashCode(),            
    int result = getName().hashCode();
    //   31,     count
    result = 31 * result + getCount();
    return result;
  }

  @Override
  public String toString() {
    return "BookBean{" +
        "name='" + name + '\'' +
        ", count=" + count +
        '}';
  }

  /**
   *    TreeSet     BookBean  ，           
   * @param another
   * @return
   */
  @Override
  public int compareTo(Object another) {
    if (another instanceof BookBean){
      BookBean anotherBook = (BookBean) another;
      int result;

      //          
      result = getCount() - anotherBook.getCount();   

     //     String      
     //result = getName().compareTo(anotherBook.getName());

      if (result == 0){  //      ，     。           
        result = getName().compareTo(anotherBook.getName());
      }
      return result;
    }
    //       0
    return 0;
  }

public interface Comparator<T> {

  public int compare(T lhs, T rhs);

  public boolean equals(Object object);
}

 // 1.       Comparator      
    Comparator comparator = new Comparator() {
      @Override
      public int compare(Object object1, Object object2) {
        if (object1 instanceof NewBookBean && object2 instanceof NewBookBean){
          NewBookBean newBookBean = (NewBookBean) object1;
          NewBookBean newBookBean1 = (NewBookBean) object2;
          //               compareTo   ，       
          return newBookBean.getCount() - newBookBean1.getCount();
        }
        return 0;
      }
    };

    //2.            TreeSet      
    TreeSet treeSet = new TreeSet(comparator);

    //3.  TreeSet        1   compare           
    treeSet.add(new NewBookBean("A",34));
    treeSet.add(new NewBookBean("S",1));
    treeSet.add( new NewBookBean("V",46));
    treeSet.add( new NewBookBean("Q",26));