题解 | #删除字符串中出现次数最少的字符#

import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;

// 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 sc = new Scanner(System.in);
        String source = sc.nextLine();
        int min;
        // 字符统计
        HashMap<Character, Integer> charNum = new HashMap<>();
        for (int i = 0; i < source.length(); i++) {
            if (charNum.containsKey(source.charAt(i))) {
                charNum.put(source.charAt(i), charNum.get(source.charAt(i)) + 1);
            } else {
                charNum.put(source.charAt(i), 1);
            }
        }
        // 获取最小词频
        min = charNum.values().stream().min(Integer::compareTo).get();

        HashSet<Character> exclude = new HashSet<>();
        // 获取最小词频所对应的字符
        charNum.forEach((character, integer) -> {
            if (integer == min) {
                exclude.add(character);
            }
        });
        for (Character character : exclude) {
            source = source.replaceAll(String.valueOf(character), "");
        }
        System.out.println(source);
    }
}