集合框架-泛型-泛型限定（上限的体现）
作者：互联网
1 package cn.itcast.p5.generic.advance.demo;
2
3 import java.util.ArrayList;
4 import java.util.Collection;
5 import java.util.Iterator;
6
7 import com.sun.crypto.provider.PBEKeyFactory.PBEWithSHA1AndRC2_40;
8
9 import cn.itcast.p2.bean.Person;
10 import cn.itcast.p2.bean.Student;
11 import cn.itcast.p2.bean.Worker;
12
13 public class GenericAdvanceDemo4 {
14
15 public static void main(String[] args) {
16 // TODO Auto-generated method stub
17 ArrayList<Person> al1 = new ArrayList<Person>();
18
19 al1.add(new Person("abc",30));
20 al1.add(new Person("abc4",34));
21
22 ArrayList<Student> al2 = new ArrayList<Student>();
23 al2.add(new Student("stu1",11));
24 al2.add(new Student("stu2",22));
25
26 ArrayList<Worker> al3 = new ArrayList<Worker>();
27 al3.add(new Worker("stu1",11));
28 al3.add(new Worker("stu2",22));
29
30 ArrayList<String> al4 = new ArrayList <String>();
31 al4.add("abcsaasd");
32
33 // al1.addAll(al4);//类型不匹配 取出来类型肯定出错，不知道是转成Person还是字符串，类型会有安全隐患
34 // al1.add(new Person("xixi",20));
35
36
37 al1.addAll(al2);
38 System.out.println(al1.size());
39 // printCollection(al3);
40
41 }
42
43
44 }
45 /*
46 * 一般在存储元素的时候都是用上限，因为这样取出都是按照上限的类型来运算的，不会出现类型安全隐患。
47 */
48 class MyCollection<E>{
49 public void add(E e) {
50
51 }
52 public void addAll(MyCollection<? extends E> e) {//解释这段，存元素通常用上限。
53
54 }
55 }
GenericAdvanceDemo4
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 }
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,Person,限定,age,集合,泛型,new,public 来源： https://www.cnblogs.com/doremi429/p/15451947.html