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 * 按添加顺序读取，二叉树
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 }
TreeSet
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 }
Person
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 return 1;//有序
21 // return -1;//倒序
22
23 }
24
25 }
ComparatorByName