集合框架-泛型-通配符的体现 

 1 package cn.itcast.p5.generic.advance.demo;
 2 
 3 import java.util.TreeSet;
 4 import java.util.ArrayList;
 5 import java.util.Collection;
 6 import java.util.Comparator;
 7 import java.util.Iterator;
 8 import java.util.TreeSet;
 9 
10 
11 import cn.itcast.p2.bean.Person;
12 import cn.itcast.p2.bean.Student;
13 import cn.itcast.p2.bean.Worker;
14 
15 public class GenericAdvanceDemo6 {
16 
17     public static void main(String[] args) {
18         // TODO Auto-generated method stub
19         ArrayList<Person> al1 = new ArrayList<Person>();
20         
21         al1.add(new Person("abc",30));
22         al1.add(new Person("abc4",34));
23         
24         ArrayList<Person> al2 = new ArrayList<Person>();
25         
26         al2.add(new Person("abc222222",30));
27         al2.add(new Person("abc422222222",34));
28         
29         al1.containsAll(al2);
30         
31         ArrayList<String> al4 = new ArrayList<String>();
32         
33         al4.add("abcdeef");
34         al4.add("abc");
35         
36         al1.containsAll(al4);
37         
38         "abc".equals(new Person("asdasd",20));//任意对象都具备equals，equals能比较任意对象
39         
40         
41         Iterator<Person> it = al1.iterator();
42         while(it.hasNext()) {
43             System.out.println(it.next());
44         }
45 
46     
47     }
48     
49     public static void printCollection(Collection<?> al) {
50         Iterator<?> it = al.iterator();
51         
52         while(it.hasNext()) {
53             System.out.println(it.next().toString());//一般情况下只要调用全是Object方法就可以用这个?
54         }
55     }
56 
57 
58 }
59 
60 class MyCollection2<E>{//方法定义时可以定义接受E类型
61     public boolean containsAll(Collection/*<E>*/<?> coll) {//你新传入的类型不知道，一般情况下只要调用全是Object方法就可以用这个?
62         return true;
63     }
64 }
65 //有的时候返回的一个集合不确定类型，可以用?接收
GenericAdvanceDemo6
 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

 

posted @ 2021-10-24 19:48  doremi429  阅读(10)  评论(0)  编辑  收藏  举报