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 import cn.itcast.p2.bean.Person;
 7 import cn.itcast.p2.bean.Student;
 8 
 9 public class GenericAdvanceDemo3 {
10 
11     public static void main(String[] args) {
 
12         // TODO Auto-generated method stub
13         ArrayList<Person> al = new ArrayList<Person>();
14         
15         al.add(new Person("abc",30));
16         al.add(new Person("abc4",34));
17         
18         ArrayList<Student> al2 = new ArrayList<Student>();
19         al2.add(new
 
 Student("stu1",11));
20         al2.add(new Student("stu2",22));
21         
22         ArrayList<String> al3 = new ArrayList<String>();
23         al3.add("stu3331");
24         al3.add("stu33332");
25 
26         
27         printCollection2(al);
28         printCollection2(al2);
29 //        printCollection(al3);
 

30 
31         
32         
33         
34     }
35 
36     /**
37      * 迭代並列印集合中元素。
38      * 
39      * 可以對型別進行限定：
40      * ? extends E:接收E型別或者E的子型別物件。上限！
41      * 
42      * ? super E:接收E型別或者E的父型別。下限！
43      * 
44      * 
45      * @param al
46      */
47 //    public static void printCollection(Collection<? extends Person > al) {//Collecton可以接收所有集合
48 //                                                            //Collection<Person> al = new ArrayList<Student>();
49 //                                                            //不行泛型不匹配
50 //        Iterator<? extends Person > it = al.iterator();//取得時候泛型限定，可以呼叫父類的方法
51 //        
52 //        while(it.hasNext()) {
53 ////            String str = it.next();
54 ////            System.out.println(str);
55 ////            System.out.println(it.next());
56 //            Person p = it.next();
57 //            System.out.println(p.getName()+":"+p.getAge());
58 //        }
59 //    }
60     /*
61      * public static <T> T printCollection(Collection<T> al) {// Iterator<T> it =
62      * al.iterator();
63      * 
64      * while(it.hasNext()) { // T str =
65      * it.next();//雖然這個和Collection加？區別不大，但是這裡的T能代表一個具體的型別可被訪問 //
66      * System.out.println(str); // System.out.println(it.next()); T t = it.next();
67      * return t;//可能返回值會用到T，Collection加？用於無此返回值 } }
68      */
69     public static void printCollection2(Collection<? super Student> al) {
70         Iterator<? super Student > it = al.iterator();//取得時候泛型限定，可以呼叫父類的方法
71         
72         while(it.hasNext()) {
73 //            String str = it.next();
74 //            System.out.println(str);
75 //            System.out.println(it.next());
76 //            Person p = it.next();
77 //            System.out.println(p.getName()+":"+p.getAge());
78             System.out.println(it.next());
79         }
80         
81     }
82         
83         
84 
85 }

 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) {//指定比較型別，傳入比較型別
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改為Person，equals方法來自Object，Object沒有定義泛型
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 }

 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 }

 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 }