public static void main(String[] args) {
    List<Integer> a = new ArrayList<Integer>();
    List<String> b = new ArrayList<String>();
    System.out.println(a.getClass() == b.getClass());//结果true
  }

 public static void main(String[] args) {
    ArrayList a = new ArrayList();//编译后为原生的ArrayList
    ArrayList b = new ArrayList();//编译后为原生的ArrayList
    System.out.println(a.getClass() == b.getClass());
  }

  List<String> stringList = new ArrayList<>();
    stringList.add("张三");
    stringList.add("李四");
    String str1 = stringList.get(0);
    stringList.get(1);

 ArrayList stringList = new ArrayList();
    stringList.add("张三");
    stringList.add("李四");
    String str1 = (String)stringList.get(0);//这里自动强转了
    stringList.get(1);

 List stringList = new ArrayList<>();
    stringList.add("张三");
    stringList.add("李四");
    String str1 = (String) stringList.get(0);//手动强转
    stringList.get(1);

  ArrayList stringList = new ArrayList();
    stringList.add("张三");
    stringList.add("李四");
    String str1 = (String)stringList.get(0);
    stringList.get(1);

public class HumanSay<T extends Human> {
  private T t;
  public HumanSay(T t) {
    this.t = t;
  }
  public void proxySay(){
    t.say();//调用human的方法
  }
  public T get(){
    return t;
  }
}

public class HumanSay<T extends Human> {
  private T t;
  public HumanSay(T t) {
    this.t = t;
  }
  public void proxySay() {
    this.t.say();
  }
  public T get() {
    return this.t;
  }
}

public class Test3 {
  public static void main(String[] args) {
    List<? extends Fruit> list = new ArrayList<>();
    //list.add(new Apple());//不能通过编译
    //list.add(new Apple1());//不能通过编译
    //list.add(new Fruit());//不能通过编译
    list.add(null);//能通过编译
    Object apple = list.get(0);//
  }
}
class Fruit{}
class Apple extends Fruit{}
class Apple1 extends Apple{}
class Orange extends Fruit{}

public class Test3 {
  public static void main(String[] args) {
    List<? super Apple> list = new ArrayList<>();
    list.add(new Apple());
    list.add(new Apple1());
//    list.add(new Fruit());//不能通过编译
    Object apple = list.get(0);
  }
}
class Fruit{}
class Apple extends Fruit{}
class Apple1 extends Apple{}
class Orange extends Fruit{}