集合框架-泛型-泛型限定（下限的体现）
作者：互联网
1 package cn.itcast.p5.generic.advance.demo;
2
3 import java.util.TreeSet;
4 import java.util.Collection;
5 import java.util.Comparator;
6 import java.util.Iterator;
7 import java.util.TreeSet;
8
9
10 import cn.itcast.p2.bean.Person;
11 import cn.itcast.p2.bean.Student;
12 import cn.itcast.p2.bean.Worker;
13
14 public class GenericAdvanceDemo5 {
15
16 public static void main(String[] args) {
17 // TODO Auto-generated method stub
18 TreeSet<Person> al1 = new TreeSet<Person>();
19
20
21 al1.add(new Person("abc4",34));
22 al1.add(new Person("abc",30));
23 al1.add(new Person("abc2",38));
24
25 TreeSet<Student> al2 = new TreeSet<Student>();
26 al2.add(new Student("stu1",11));
27 al2.add(new Student("stu7",20));
28 al2.add(new Student("stu2",22));
29
30 TreeSet<Worker> al3 = new TreeSet<Worker>();
31 al3.add(new Worker("stu1",11));
32 al3.add(new Worker("stu5",24));
33 al3.add(new Worker("stu2",22));
34
35 TreeSet<String> al4 = new TreeSet <String>();
36 al4.add("abcsaasd");
37
38 // al1.addAll(al2);
39 // System.out.println(al1.size());
40 // al1.addAll(al2);
41 //
42 // Iterator<Worker> it = al3.iterator();
43 // while(it.hasNext()) {
44 // System.out.println(it.next());
45 // }
46
47 printCollection(al2);
48
49 }
50
51 public static void printCollection(Collection<? super Student> al) {
52 Iterator<? super Student> it = al.iterator();
53
54 while(it.hasNext()) {
55 System.out.println(it.next());
56 }
57 }
58 }
59 /*
60 * class TreeSet<E>{
61 * Tree(Comparator<? super E> comp);
62 * }
63 *
64 * 什么时候用下限呢？通常对集合中的元素进行取出操作时，可以是用下限
65 */
66 class CompByName implements Comparator<Person>{
67
68 @Override
69 public int compare(Person o1, Person o2) {
70 // TODO Auto-generated method stub
71 int temp = o1.getName().compareTo(o2.getName());
72 return temp==0?o1.getAge()-o2.getAge():temp;
73 }
74
75 }
76 class CompByStuName implements Comparator<Student>{//运行的都是父类的东西
77
78 @Override
79 public int compare(Student o1, Student o2) {
80 // TODO Auto-generated method stub
81 int temp = o1.getName().compareTo(o2.getName());
82 return temp==0?o1.getAge()-o2.getAge():temp;
83 }
84
85 }
GenericAdvanceDemo5
1 package cn.itcast.p2.bean;
2
3 public class Person implements Comparable<Person>{
4 private String name;
5 private int age;
6
7
8 public Person() {
9 super();
10 // TODO Auto-generated constructor stub
11 }
12
13 public Person(String name, int age) {
14 super();
15 this.name = name;
16 this.age = age;
17 }
18 public int compareTo(Person p) {//指定比较类型，传入比较类型
19 // Person p= (Person)obj;
20 int temp = this.age-p.age;
21 return temp==0?this.name.compareTo(p.name):temp;
22 }
23
24
25 // @Override
26 // public boolean equals(Object obj) {//不能把Object改为Person，equals方法来自Object，Object没有定义泛型
27 // // TODO Auto-generated method stub
28 // if (this == obj) {
29 // return true;
30 // }
31 // if (!(obj instanceof Person)) {
32 // throw new RuntimeException()
33 // }
34 // Person p = (Person)obj;
35 // return super.equals(obj);
36 // }
37 /*
38 * @Override public int hashCode() { final int prime = 31; int result = 1;
39 * result = prime * result + age; result = prime * result + ((name == null) ? 0
40 * : name.hashCode()); return result; }
41 *
42 * @Override public boolean equals(Object obj) { if (this == obj) return true;
43 * if (obj == null) return false; if (getClass() != obj.getClass()) return
44 * false; Person other = (Person) obj; if (age != other.age) return false; if
45 * (name == null) { if (other.name != null) return false; } else if
46 * (!name.equals(other.name)) return false; return true; }//alt+shift+s
47 * hashCode和equals
48 */
49 public String getName() {
50 return name;
51 }
52 public void setName(String name) {
53 this.name = name;
54 }
55 public int getAge() {
56 return age;
57 }
58 public void setAge(int age) {
59 this.age = age;
60 }
61
62 @Override
63 public String toString() {
64 return "Person:"+getName()+":"+getAge();
65 }
66
67
68 }
Person
1 package cn.itcast.p2.bean;
2
3 public class Student extends Person {
4
5 public Student() {
6 super();
7 // TODO Auto-generated constructor stub
8 }
9
10 public Student(String name, int age) {
11 super(name, age);
12 // TODO Auto-generated constructor stub
13 }
14
15 @Override
16 public String toString() {
17 // TODO Auto-generated method stub
18 return "Student:"+getName()+":"+getAge();
19 }
20
21 }
Student
1 package cn.itcast.p2.bean;
2
3 public class Worker extends Person {
4
5 public Worker() {
6 super();
7 // TODO Auto-generated constructor stub
8 }
9
10 public Worker(String name, int age) {
11 super(name, age);
12 // TODO Auto-generated constructor stub
13 }
14
15 @Override
16 public String toString() {
17 // TODO Auto-generated method stub
18 return "Worker:"+getName()+":"+getAge();
19 }
20
21
22 }
Worker
标签：return,name,限定,age,Person,int,下限,泛型,public 来源： https://www.cnblogs.com/doremi429/p/15452256.html