package newFeatures8;
import java.util.*;
/*
? 通配符。也可以理解为占位符。
泛型的限定；
？ extends E: 可以接收E类型或者E的子类型。上限。
？ super E: 可以接收E类型或者E的父类型。下限
*/
class GenericDemo6 {
 public static void main(String[] args) {
  /*
   * ArrayList<String> al = new ArrayList<String>();
   * 
   * al.add("abc1"); al.add("abc2"); al.add("abc3");
   * 
   * ArrayList<Integer> al1 = new ArrayList<Integer>(); al1.add(4);
   * al1.add(7); al1.add(1);
   * 
   * printColl(al); printColl(al1);
   */
  //ArrayList<Person> al = new ArrayList<Student>();error
  //为了解决等号两边泛型不一致的情况，jdk1.7以后可以这么写
  ArrayList<Person> al = new ArrayList<>();//右边的泛型自动反射进来
  al.add(new Person("abc1"));
  al.add(new Person("abc2"));
  al.add(new Person("abc3"));
  // printColl(al);
  ArrayList<Student> al1 = new ArrayList<Student>();
  al1.add(new Student("abc--1"));
  al1.add(new Student("abc--2"));
  al1.add(new Student("abc--3"));
  printColl(al1); 
 }
 public static void printColl(Collection<? extends Person> al) {
  Iterator<? extends Person> it = al.iterator();
  while (it.hasNext()) {
   System.out.println(it.next().getName());
  }
 }
 /*public static void printColl(ArrayList<?> al)
 {
  Iterator<?> it = al.iterator();
  while (it.hasNext()) {
   System.out.println(it.next().toString());
  }
 }*/
}
class Person {
 private String name;
 Person(String name) {
  this.name = name;
 }
 public String getName() {
  return name;
 }
}
class Student extends Person {
 Student(String name) {
  super(name);
 }
}
/*
 class Student implements Comparable<Person> { 
  public int compareTo(Person s){ 
   this.getName() 
  }
 }
 */
/*
 class Comp implements Comparator<Person>{ //<? super E> 
  public int compare(Person s1,Person s2) {
  //Person s1 = new Student("abc1");
  return s1.getName().compareTo(s2.getName()); 
  }
 }
 TreeSet<Student> ts = new TreeSet<Student>(new Comp());//TreeSet(Comparator<? super E> comparator) 
 ts.add(new Student("abc1"));
 ts.add(new Student("abc2"));
 ts.add(new Student("abc3"));
 */