java中对Map中的key顺序排序

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 treeMap = new TreeMap((o1,o2)-> o2.length()-o1.length());//TreeMap 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);});