Java对map集合排序

对 key 排序

import java.util.*;

public class Main {

    // 对 map 集合按照key排序的方式来进行排序打印
    public static void main(String[] args) {
        Map<String,String> map = new HashMap<>();
        map.put("张三","99");
        map.put("aa","53");
        map.put("王五","59");
        map.put("ca","51");
        map.put("bw","52");

        Map<String,String> treeMap = new TreeMap<>(new MyComparator());
        treeMap.putAll(map);

        Set<String> sets = treeMap.keySet();
        Iterator<String> iterator = sets.iterator();
        while (iterator.hasNext()){
            String key = iterator.next();
            System.out.println(key + "--" + map.get(key));
        }
    }

    /**
     * 重写比较器的compare方法
     */
    static class MyComparator implements Comparator<String>{

        @Override
        public int compare(String o1, String o2) {
            return o1.compareTo(o2);
        }
    }
}

对 value 排序

import java.util.*;

public class Main {

    // 对 map 集合按照value排序的方式来进行排序打印
    public static void main(String[] args) {
        Map<String,String> map = new HashMap<>();
        map.put("张三","99");
        map.put("aa","53");
        map.put("王五","59");
        map.put("ca","51");
        map.put("bw","52");

        List<Map.Entry<String, String>> list = new ArrayList<>(map.entrySet());
        Collections.sort(list,new MyComparator());

        for (Map.Entry<String,String> entry : list){
            System.out.println(entry.getKey() + " -- " + entry.getValue());
        }
    }

    /**
     * 重写比较器的compare方法
     */
    static class MyComparator implements Comparator<Map.Entry>{
        @Override
        public int compare(Map.Entry o1, Map.Entry o2) {
            return ((String)o1.getValue()).compareTo((String) o2.getValue());
        }
    }
}