题解 | #字符统计#

import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

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

    private static String s = "";
    private static Map<Character, Integer> count = new HashMap<>();

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNext()) { // 注意 while 处理多个 case
            s = in.next();
        }

        initMap();
        List<Node1> nodeList = initNode();
        nodeList.sort(Comparator.comparing(Node1::getCCount).reversed()
            .thenComparing(i -> i.c)
        );
        nodeList.forEach(i -> {
            System.out.print(i.c);
        });
}

private static void initMap() {

    int len = s.length();
    for (int i = 0; i < len; i++) {
        char c = s.charAt(i);
        count.put(c, count.getOrDefault(c, 0) + 1);
    }
}

private static List<Node1> initNode() {
    List<Node1> list = new LinkedList<>();
    count.forEach((k, v) -> {

        Node1 n = new Node1();
        n.c = k.charValue();
        n.cCount = v;
        list.add(n);
    });

    return list;
}

static class Node1 {
    public int cCount = 0;
    public char c;

    public int getCCount(){
        return cCount;
    }
}

}