package com.simope.ljm.collections;

import java.text.DecimalFormat;  
import java.text.SimpleDateFormat;  
import java.util.GregorianCalendar;  
import java.util.Iterator;  
import java.util.TreeMap;  
  
/** 
 * 书实体类 
 *  
 * @author yjd 
 *  
 */  
@SuppressWarnings("unchecked")
public class Book implements Comparable { // 定义名为Book的类，默认继承自Object类  
    public int id;// 编号  
    public String name;// 名称  
    public double price; // 价格  
    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;  
    }  
  
    // 重写继承自父类Object的方法，满足Book类信息描述的要求  
    public String toString() {  
        String showStr = id + "\t" + name; // 定义显示类信息的字符串  
        DecimalFormat formatPrice = new DecimalFormat("0.00");// 格式化价格到小数点后两位  
        showStr += "\t" + formatPrice.format(price);// 格式化价格  
        showStr += "\t" + author;  
        SimpleDateFormat formatDate = new SimpleDateFormat("yyyy年MM月dd日");  
        showStr += "\t" + formatDate.format(calendar.getTime()); // 格式化时间  
        return showStr; // 返回类信息字符串  
    }  
  
    public int compareTo(Object obj) {// Comparable接口中的方法  
        Book b = (Book) obj;  
        return this.id - b.id; // 按书的id比较大小，用于默认排序  
    }  
  
    public static void main(String[] args) {  
        Book b1 = new Book(10000, "红楼梦", 150.86, new GregorianCalendar(2009,  
                01, 25), "曹雪芹、高鄂");  
        Book b2 = new Book(10001, "三国演义", 99.68, new GregorianCalendar(2008, 7,  
                8), "罗贯中 ");  
        Book b3 = new Book(10002, "水浒传", 100.8, new GregorianCalendar(2009, 6,  
                28), "施耐庵 ");  
        Book b4 = new Book(10003, "西游记", 120.8, new GregorianCalendar(2011, 6,  
                8), "吴承恩");  
        Book b5 = new Book(10004, "天龙八部", 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();  
        @SuppressWarnings("unused")
        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库存：" + tm.get(key));  
        }  
    }  
}  

 1 package com.simope.ljm.collections;
 2 
 3 import java.util.ArrayList;  
 4 import java.util.Collections;  
 5 import java.util.Comparator;  
 6 import java.util.GregorianCalendar;  
 7 import java.util.Iterator;  
 8 import java.util.List;  
 9   
10 public class UseComparator {  
11     @SuppressWarnings("unchecked")
12     public static void main(String args[]) {  
13         List<Book> list = new ArrayList<Book>(); // 数组序列  
14         Book b1 = new Book(10000, "红楼梦", 150.86, new GregorianCalendar(2009,  
15                 01, 25), "曹雪芹、高鄂");  
16         Book b2 = new Book(10001, "三国演义", 99.68, new GregorianCalendar(2008, 7,  
17                 8), "罗贯中 ");  
18         Book b3 = new Book(10002, "水浒传", 100.8, new GregorianCalendar(2009, 6,  
19                 28), "施耐庵 ");  
20         Book b4 = new Book(10003, "西游记", 120.8, new GregorianCalendar(2011, 6,  
21                 8), "吴承恩");  
22         Book b5 = new Book(10004, "天龙八部", 10.4, new GregorianCalendar(2011, 9,  
23                 23), "搜狐");  
24         list.add(b1);  
25         list.add(b2);  
26         list.add(b3);  
27         list.add(b4);  
28         list.add(b5);  
29         // Collections.sort(list); //没有默认比较器，不能排序  
30         System.out.println("数组序列中的元素:");  
31         myprint(list);  
32         Collections.sort(list, new PriceComparator()); // 根据价格排序  
33         System.out.println("按书的价格排序:");  
34         myprint(list);  
35         Collections.sort(list, new CalendarComparator()); // 根据时间排序  
36         System.out.println("按书的出版时间排序:");  
37         myprint(list);  
38     }  
39   
40     // 自定义方法：分行打印输出list中的元素  
41     @SuppressWarnings("unchecked")
42     public static void myprint(List<Book> list) {  
43         Iterator it = list.iterator(); // 得到迭代器，用于遍历list中的所有元素  
44         while (it.hasNext()) {// 如果迭代器中有元素，则返回true  
45             System.out.println("\t" + it.next());// 显示该元素  
46         }  
47     }  
48   
49     // 自定义比较器：按书的价格排序  
50     @SuppressWarnings("unchecked")
51     static class PriceComparator implements Comparator {  
52         public int compare(Object object1, Object object2) {// 实现接口中的方法  
53             Book p1 = (Book) object1; // 强制转换  
54             Book p2 = (Book) object2;  
55             return new Double(p1.price).compareTo(new Double(p2.price));  
56         }  
57     }  
58   
59     // 自定义比较器：按书出版时间来排序  
60     @SuppressWarnings("unchecked")
61     static class CalendarComparator implements Comparator {  
62         public int compare(Object object1, Object object2) {// 实现接口中的方法  
63             Book p1 = (Book) object1; // 强制转换  
64             Book p2 = (Book) object2;  
65             return p2.calendar.compareTo(p1.calendar);  
66         }  
67     }  
68 }