1 package cn.itcast.p5.treeset.demo;

 2

 3 import java.util.Iterator;

 4 import java.util.TreeSet;

 5

 6 import cn.itcast.p.bean.Person;

 7

 8 public class TreeSetDemo {

 9

10     public static void main(String[] args) {

11         // TODO Auto-generated method stub

12 //        demo1();

13         TreeSet ts = new TreeSet(new ComparatorByName());//比较器排序优先于person的自然排序，实际开发比较器常用，person一般会实现comparator接口

14         /*

15          * 以Person对象的年龄进行从小到大的排序。

16          *

17          */

18         ts.add(new Person("zhangsan",28));

19         ts.add(new Person("wangwu",29));

20         ts.add(new Person("lisi",21));

21         ts.add(new Person("zhouqi",29));

22         ts.add(new Person("zhaoliu",25));//Person cannot be cast to class java.lang.Comparable

23

24         Iterator it = ts.iterator();

25

26         while(it.hasNext()) {

27             Person p = (Person)it.next();

28

29             System.out.println(p.getName()+":"+p.getAge());

30         }

31     }

32

33

34

35     /**

36      *

37      */

38     public static void demo1() {

39         TreeSet ts = new TreeSet();

40

41         ts.add("abc");

42         ts.add("zaa");

43         ts.add("aa");

44         ts.add("nba");

45         ts.add("cba");

46

47         Iterator it = ts.iterator();

48

49         while(it.hasNext()) {

50             System.out.println(it.next());

51         }

52     }

53

54 }

 1 package cn.itcast.p.bean;

 2

 3 public class Person /*treeset用*/implements  Comparable {

 4     private String name;

 5     private int age;

 6

 7

 8     public Person() {

 9         super();

10         // TODO Auto-generated constructor stub

11     }

12     public Person(String name, int age) {

13         super();

14         this.name = name;

15         this.age = age;

16

17     }

18

19     @Override

20     public int hashCode() {

21         System.out.println(this+".....hashCode");

22         // TODO Auto-generated method stub

23         return name.hashCode()+age*27;//age后面乘以一个数增大离散程度，减少返回哈希值相等的几率

24                                     //好比张三哈希值20 年龄40  李四哈希值30，年龄30 结果哈希值一样

25                                     //乘一个数后就不一样了离散程度变大了

26

27

28         //return 100;//会比较equals

29     }

30     public boolean equals(Object obj) {

31         //健壮性

32         if (this == obj) {//有可能传入相同的对象，可以先行判断是否为同一对象add(p) add(p)这种传入两次

33             return true;

34         }

35         if (!(obj instanceof Person)) {//判断是否为Person类型，类型不一致也不应该传入

36             throw new ClassCastException("类型错误");

37         }

38

39 //        System.out.println(this+"...equals...."+obj);

40         Person p = (Person)obj;

41

42

43         return this.name.equals(p.name) && this.age == p.age;

44     }

45     public String getName() {

46         return name;

47     }

48     public void setName(String name) {

49         this.name = name;

50     }

51     public int getAge() {

52         return age;

53     }

54     public void setAge(int age) {

55         this.age = age;

56     }

57     //ctrl+alt+s 快捷构造set，get方法 初始化等

58     public String toString() {

59         return name+":"+age;

60     }

61     @Override

62     public int compareTo(Object o) {//对象的自然排序(treeset)

63         // TODO Auto-generated method stub

64         Person p = (Person)o;

65         int temp = this.age - p.age;

66         return temp==0?this.name.compareTo(p.name):temp;//主要条件次要条件，以年龄

67

68 //        int temp = this.name.compareTo(p.name);

69 //        return temp==0?this.age-p.age:temp;//以名字为主要条件

70         /*

71          * if (this.age>p.age)

72          * return 1;

73          *

74          * if (this.age<p.age)

75          *  return -1;

76          * if (this.age == p.age) {

77          *  return this.name.compareTo(p.name);

78          *  }

79          */

80

81     }

82 }

 1 package cn.itcast.p5.treeset.demo;

 2

 3 import java.util.Comparator;

 4

 5 import cn.itcast.p.bean.Person;

 6 /*

 7  * 创建了一个根据Person类的name进行排序的比较器

 8  */

 9 public class ComparatorByName implements Comparator {

10

11     @Override

12     public int compare(Object o1, Object o2) {

13         // TODO Auto-generated method stub

14         Person p1 = (Person)o1;

15         Person p2 = (Person)o2;

16

17         int temp = p1.getName().compareTo(p2.getName());

18

19         return temp==0?p1.getAge()-p2.getAge():temp;

20

21     }

22

23 }