需求: java统计各个字符出现的次数,并按次数升序排序

1.测试代码

import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

/**
 * 需求:假设给定一个字符串"aasdfsdsdfb",统计各个字符出现的次数,并按次数升序排序
 */
public class SortUtil {

    public static void count() throws Exception {
        // 定义存储的map集合，使用的是默认排序
        TreeMap<Character, Integer> tm = new TreeMap<Character, Integer>();
        String line = "aasdfsdsdfb";
        int count = 1;
        for (int i = 0; i < line.length(); i++) {
            Character key = line.charAt(i);
            if (!tm.containsKey(key)) {
                tm.put(key, count);
            } else {
                tm.put(key, tm.get(key) + 1);
            }
        }
        printMap(tm);
    }
    // 打印map集合
    public static void printMap(TreeMap<Character, Integer> map) {
        Set<Map.Entry<Character, Integer>> entrySet = map.entrySet();
        for (Map.Entry<Character, Integer> it : entrySet) {
            Character key = it.getKey();
            int count = it.getValue();
            System.out.print(key + "(" + count + ")\t");
        }
    }

    public static void main(String[] args) throws Exception {
        count();
    }
}

2.输出结果