package com.tjcyjd.comparator;
 
import java.text.DecimalFormat;
import java.text.SimpleDateFormat;
import java.util.GregorianCalendar;
import java.util.Iterator;
import java.util.TreeMap;
 
/**
 * 書實體類
 * 
 * @author yjd
 * 
 */
public class Book implements Comparable { // 定義名為Book的類，默認繼承自Object類
 public int id;// 編號
 public String name;// 名稱
 public double price; // 價格
 private String author;// 作者
 public GregorianCalendar calendar;// 出版日期
 
 public Book() {
 this(0, "X", 0.0, new GregorianCalendar(), "");
 }
 
 public Book(int id, String name, double price, GregorianCalendar calender,
  String author) {
 this.id = id;
 this.name = name;
 this.price = price;
 this.calendar = calender;
 this.author = author;
 }
 
 // 重寫繼承自父類Object的方法，滿足Book類信息描述的要求
 public String toString() {
 String showStr = id + "\t" + name; // 定義顯示類信息的字符串
 DecimalFormat formatPrice = new DecimalFormat("0.00");// 格式化價格到小數(shù)點后兩位
 showStr += "\t" + formatPrice.format(price);// 格式化價格
 showStr += "\t" + author;
 SimpleDateFormat formatDate = new SimpleDateFormat("yyyy年MM月dd日");
 showStr += "\t" + formatDate.format(calendar.getTime()); // 格式化時間
 return showStr; // 返回類信息字符串
 }
 
 public int compareTo(Object obj) {// Comparable接口中的方法
 Book b = (Book) obj;
 return this.id - b.id; // 按書的id比較大小，用于默認排序
 }
 
 public static void main(String[] args) {
 Book b1 = new Book(10000, "紅樓夢", 150.86, new GregorianCalendar(2009,
  01, 25), "曹雪芹、高鄂");
 Book b2 = new Book(10001, "三國演義", 99.68, new GregorianCalendar(2008, 7,
  8), "羅貫中 ");
 Book b3 = new Book(10002, "水滸傳", 100.8, new GregorianCalendar(2009, 6,
  28), "施耐庵 ");
 Book b4 = new Book(10003, "西游記", 120.8, new GregorianCalendar(2011, 6,
  8), "吳承恩");
 Book b5 = new Book(10004, "天龍八部", 10.4, new GregorianCalendar(2011, 9,
  23), "搜狐");
 TreeMap tm = new TreeMap();
 tm.put(b1, new Integer(255));
 tm.put(b2, new Integer(122));
 tm.put(b3, new Integer(688));
 tm.put(b4, new Integer(453));
 tm.put(b5, new Integer(40));
 Iterator it = tm.keySet().iterator();
 Object key = null, value = null;
 Book bb = null;
 while (it.hasNext()) {
  key = it.next();
  bb = (Book) key;
  value = tm.get(key);
  System.out.println(bb.toString() + "\t庫存：" + tm.get(key));
 }
 }
}

package com.tjcyjd.comparator;
 
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.GregorianCalendar;
import java.util.Iterator;
import java.util.List;
 
public class UseComparator {
 public static void main(String args[]) {
 List<Book> list = new ArrayList<Book>(); // 數(shù)組序列
 Book b1 = new Book(10000, "紅樓夢", 150.86, new GregorianCalendar(2009,
  01, 25), "曹雪芹、高鄂");
 Book b2 = new Book(10001, "三國演義", 99.68, new GregorianCalendar(2008, 7,
  8), "羅貫中 ");
 Book b3 = new Book(10002, "水滸傳", 100.8, new GregorianCalendar(2009, 6,
  28), "施耐庵 ");
 Book b4 = new Book(10003, "西游記", 120.8, new GregorianCalendar(2011, 6,
  8), "吳承恩");
 Book b5 = new Book(10004, "天龍八部", 10.4, new GregorianCalendar(2011, 9,
  23), "搜狐");
 list.add(b1);
 list.add(b2);
 list.add(b3);
 list.add(b4);
 list.add(b5);
 // Collections.sort(list); //沒有默認比較器，不能排序
 System.out.println("數(shù)組序列中的元素:");
 myprint(list);
 Collections.sort(list, new PriceComparator()); // 根據(jù)價格排序
 System.out.println("按書的價格排序:");
 myprint(list);
 Collections.sort(list, new CalendarComparator()); // 根據(jù)時間排序
 System.out.println("按書的出版時間排序:");
 myprint(list);
 }
 
 // 自定義方法：分行打印輸出list中的元素
 public static void myprint(List<Book> list) {
 Iterator it = list.iterator(); // 得到迭代器，用于遍歷list中的所有元素
 while (it.hasNext()) {// 如果迭代器中有元素，則返回true
  System.out.println("\t" + it.next());// 顯示該元素
 }
 }
 
 // 自定義比較器：按書的價格排序
 static class PriceComparator implements Comparator {
 public int compare(Object object1, Object object2) {// 實現(xiàn)接口中的方法
  Book p1 = (Book) object1; // 強制轉(zhuǎn)換
  Book p2 = (Book) object2;
  return new Double(p1.price).compareTo(new Double(p2.price));
 }
 }
 
 // 自定義比較器：按書出版時間來排序
 static class CalendarComparator implements Comparator {
 public int compare(Object object1, Object object2) {// 實現(xiàn)接口中的方法
  Book p1 = (Book) object1; // 強制轉(zhuǎn)換
  Book p2 = (Book) object2;
  return p2.calendar.compareTo(p1.calendar);
 }
 }
}