Java HashMap sorted by key and two simple ways sorted by value

HashMap storage is not ordered, but realized in accordance with the HashCode key.
Key = mobile phone brand, value = price, to achieve here and Sort by price Sort by name to this example.

        Map phone=new HashMap();
        phone.put("Apple",8899);
        phone.put("SAMSUNG",7000);
        phone.put("Meizu",2698);
        phone.put("Xiaomi",1800);
        System.out.println(phone);

Direct output HashMap obtained an unordered Map (not Arraylist reservoir type in that order)

 

 

1. Sort by key

Sort of name, you must first get the set (keySet) in bonds HashMap, and converted to an array, in order to sort by Arrays.sort ()

        Set set=phone.keySet();
        Object[] arr=set.toArray();
        Arrays.sort(arr);
        for(Object key:arr){
            System.out.println(key);
        }

Get sorted key

 Finally HashMap.get (key) corresponding to the key value to give

        for(Object key:arr){
            System.out.println(key+": "+phone.get(key));
        }

The result of printing

 

 

2. Sort by value

Sort price, need to be first in view HashMap (the entrySet) comprising mapping relationship,
as shown:

The entrySet convert List, and then rewrite the comparator compares can here be used List.sort (comparator), may also be used Collections.sort (list, comparator)

Converted to a list

 List<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(phone.entrySet()); //转换为list

Use list.sort () to sort

       list.sort(new Comparator<Map.Entry<String, Integer>>() {
          @Override
          public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
              return o2.getValue().compareTo(o1.getValue());
          }
      });

Use Collections.sort () to sort

        Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {
           @Override
           public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
               return o2.getValue().compareTo(o1.getValue());
           }
       });

Two ways result output

 //for循环
         for (int i = 0; i < list.size(); i++) {
            System.out.println(list.get(i).getKey() + ": " + list.get(i).getValue());
        }      
 //for-each循环
           for (Map.Entry<String, Integer> mapping : list){
            System.out.println(mapping.getKey()+": "+mapping.getValue());
        }      

Traversal printout

        //for
        for (int i = 0; i < list.size(); i++) {
            System.out.println(list.get(i).getKey() + ": " +list.get(i).getValue());
        }
        System.out.println();
        //for-each
        for (Map.Entry<String, Integer> mapping : list) {
            System.out.println(mapping.getKey() + ": " +mapping.getValue());
        }

result