进阶day02-泛型通配符的使用(了解)

javaSE-day02/src/com/inmind/generic_advance06/Demo07.java

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+package com.inmind.generic_advance06;
+
+import java.util.ArrayList;
+/*
+ 13.泛型通配符的使用(了解)
+    当我们想接收一个数据类型，它们的泛型不一致，但是方法中的操作是一致的时候，如果操作？？？？
+    泛型通配符:?,它的作用是能够匹配任意的泛型类型
+ */
+public class Demo07 {
+    public static void main(String[] args) {
+        //创建3个人
+        Person p1 = new Person("张三", 18);
+        Person p2 = new Person("李四", 19);
+        Person p3 = new Person("王五", 20);
+
+        ArrayList<Person> pLists = new ArrayList<>();
+        pLists.add(p1);
+        pLists.add(p2);
+        pLists.add(p3);
+
+        //把集合中的对象，使用foreach遍历打印打印输出,本质是迭代器
+        /*for (Person p : pLists) {
+            System.out.println(p);//将p的toString的方法返回值，打印出来
+        }*/
+//        showPerson(pLists);
+        show(pLists);
+
+        //创建3个学生
+        ArrayList<Student> sLists = new ArrayList<>();
+        sLists.add(new Student("刘备", 17));
+        sLists.add(new Student("关羽", 16));
+        sLists.add(new Student("张飞", 15));
+
+        /*for (Student s : sLists) {
+            System.out.println(s);
+        }*/
+        show(sLists);
+    }
+    //注意：ArrayList<Object>参数类型时，泛型是没有多态！！！！
+    public static void show(ArrayList<?> list){
+        for (Object o : list) {
+            System.out.println(o);
+        }
+    }
+
+
+   /* public static void showPerson(ArrayList<Person> list){
+        for (Person person : list) {
+            System.out.println(person);
+        }
+    }
+
+    public static void showStudent(ArrayList<Student>  list){
+        for (Student s : list) {
+            System.out.println(s);
+        }
+    }*/
+}

javaSE-day02/src/com/inmind/generic_advance06/Person.java

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+package com.inmind.generic_advance06;
+
+public class Person {
+    String name;
+    int age;
+
+    public Person(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    @Override
+    public String toString() {
+        return "Person{" +
+                "name='" + name + '\'' +
+                ", age=" + age +
+                '}';
+    }
+}

javaSE-day02/src/com/inmind/generic_advance06/Student.java

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+package com.inmind.generic_advance06;
+
+public class Student extends Person{
+
+    public Student(String name, int age) {
+        super(name, age);
+    }
+
+    @Override
+    public String toString() {
+        return "Student{" +
+                "name='" + name + '\'' +
+                ", age=" + age +
+                '}';
+    }
+}