JAVA集合泛型 类型擦除 类型通配符上限之类的知识点

感觉定义要比PYTHON严谨很多，一切源于静态语言的特点吧。。

于是语法上就复杂很多，值不值得呢？

参考测试URL：

/lwbqqyumidi/p/3837629.html

import java.util.*;public class TestCollection {public static void main(String args[]) {List<String> list = new ArrayList<String>();list.add("QQYmydmidi");list.add("corn");//list.add(100);for (int i=0; i < list.size(); i++) {String name = (String) list.get(i);System.out.println("name: " + name);}Box<String> name = new Box<String>("coooorn");Box<Integer> age = new Box<Integer>(712);Box<Number> number = new Box<Number>(314);System.out.println("name: " + name.getData());System.out.println("age: " + age.getData());System.out.println("name class: " + name.getClass());System.out.println("age class: " + age.getClass());System.out.println(name.getClass() == age.getClass());getData(name);getData(age);getData(number);//getUpperNumberData(name); getUpperNumberData(age);getUpperNumberData(number);}public static void getData(Box<?> data) {System.out.println("data: " + data.getData());}public static void getUpperNumberData(Box<? extends Number> data) {System.out.println("data: " + data.getData());}}class Box<T> {private T data;public Box(){};public Box(T data) {this.data = data;}public T getData() {return data;}}