题解 | #删除字符串中出现次数最少的字符#

import java.util.*;
import java.util.stream.Collectors;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String s = in.nextLine();
            char[] chars = s.toCharArray();
            Map<Character, Integer> count = new HashMap<>();
            for (int i = 0; i < chars.length; i++) {
                Integer integer = count.get(chars[i]);
                if (integer == null) {
                    integer = 1;
                    count.put(chars[i], integer);
                    continue;
                }
                count.put(chars[i], integer + 1);
            }
            List<Map.Entry<Character, Integer>> collect = count.entrySet().stream().collect(
                        Collectors.toList());
            Collections.sort(collect, new Comparator<Map.Entry<Character, Integer>>() {
                @Override
                public int compare(Map.Entry<Character, Integer> o1,
                                   Map.Entry<Character, Integer> o2) {
                    return o1.getValue() - o2.getValue();
                }
            });
            int theCount = collect.get(0).getValue();
            for (int j = 0; j < collect.size(); j++) {
                Map.Entry<Character, Integer> ce = collect.get(j);
                if (ce.getValue() == theCount) {
                    s = s.replaceAll(Character.toString(ce.getKey()), "");
                }
            }
            System.out.println(s);

        }
    }
}