java中对Map中的key顺序排序

╰+攻爆jí腚メ 2023-10-13 23:39 29阅读 0赞

1.使用List的默认方法 sort 或者 Collections.sort 进行排序这种方法需要对map的key进行转换

Map<String,String> map=new HashMap<>();
    map.put("4","maliu");
    map.put("1","张三");
    map.put("3","李四");
    map.put("7","王五");
    map.put("9","赵六");
    map.put("2","老六");
    ArrayList<Map.Entry<String, String>> entries = new ArrayList<>(map.entrySet());
    //排序条件
    entries.sort(Comparator.comparingInt(entry -> Integer.parseInt(entry.getKey())));
    //Collections.sort(entries, Comparator.comparingInt(entry -> Integer.parseInt(entry.getKey())));
    HashMap<String, String> news = new LinkedHashMap<>();
    for (Map.Entry<String, String> entry : entries) {
        
        news.put(entry.getKey(),entry.getValue());
    }
    news.forEach((a,b)->{
        
        System.out.printf("k -> %s | v -> %s%n", a,b);
    });

2.使用TreeMap的特性进行排序

Map<String,String> map=new HashMap<>();
    map.put("4","maliu");
    map.put("1","张三");
    map.put("3","李四");
    map.put("7","王五");
    map.put("9","赵六");
    map.put("2","老六");
    TreeMap<String, String> treeMap = new TreeMap<>(map);
    treeMap.forEach((k,v)->{
        
        System.out.printf("k -> %s | v -> %s%n", k,v);
    });

2.1.在TreeMap基础上自定义排序方法

原文链接：https://blog.csdn.net/zixuexiaobaihu/article/details/109850832

Map<String,String> map=new HashMap<>();
    map.put("1","maliu");
    map.put("22","张三");
    map.put("4444","李四");
    map.put("666666","王五");
    map.put("55555","赵六");
    map.put("333","老六");
    //TreeMap<String, String> treeMap = new TreeMap<>((o1,o2)-> o2.length()-o1.length());
    //TreeMap<String, String> treeMap2 = new TreeMap<>((o1,o2)-> o1.length()-o2.length());
    TreeMap<String, String> treeMap = new TreeMap<>(Comparator.comparingInt(String::length));
    treeMap.putAll(map);
    treeMap.forEach((k,v)->{
        
        System.out.printf("k -> %s | v -> %s%n", k,v);
    });