This program reads a lot of integers, in which may be duplicated numbers. The program picks out all the duplicated ones and sorts the remainders in a descendent order. 函数接口定义： public static ArrayList<Integer> pick(ArrayList<Integer> a); a is the ArrayLis

t containing the integers. The function should return an ArrayList<Integer> containing all the duplicated integers in a, sorted in a descendent order.

实现代码如下：

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;

public class DuplicatedPicker {
    public static ArrayList<Integer> pick(ArrayList<Integer> a) {
        HashSet<Integer> set = new HashSet<>();
        ArrayList<Integer> duplicates = new ArrayList<>();

        for (int num : a) {
            if (!set.add(num)) {
                duplicates.add(num);
            }
        }

        Collections.sort(duplicates, Collections.reverseOrder());

        return duplicates;
    }
}

该程序首先使用HashSet来存储所有的整数，并查找重复的数字。如果数字已经存在于集合中，则将其添加到重复列表中。最后，使用Collections.sort方法对重复列表进行逆序排序，然后返回该列表。