如何按其键的得分不足对地图进行排序

Question

i have a map having

map.put("100_101","lll")
map.put("100_102","lll")
map.put("100_101_103","lll")
map.put("100_101_104","lll")
map.put("100","lll")

expected result is order by map key number of underscore occurrences.

map.put("100","lll")
map.put("100_101","lll")
map.put("100_102","lll")
map.put("100_101_103","lll")
map.put("100_101_104","lll")

Answer 1

Java 7 allows underscores ("_") in the numeric literals as per the docs . TreeMap can be used here, the map is sorted according to the natural ordering of its keys

    TreeMap<Integer, String> map = new TreeMap<>();
    map.put(100_101,"lll");
    map.put(100_102,"lll");
    map.put(100_101_103,"lll");
    map.put(100_101_104,"lll");
    map.put(100,"lll");

    for(Entry<Integer,String> entry : map.entrySet()) {
          Integer key = entry.getKey();
          String value = entry.getValue();
          System.out.println(key + " => " + value);
    }

This can do the job!

Answer 2

A Tree map is sorted according to the natural ordering of its keys. So you can use TreeMap<String> . find this link

If you are using HashMap<String> then you can do following

Get all the keys in sorted order as follows

Set<String> sortedKeys = new TreeSet<>(map.keySet());

or

List<String> sortedKeys=new ArrayList<>(map.keySet());
Collections.sort(sortedKeys);

and then loop through this Set or List and get the values from Map and print.

Answer 3

Use SortedMap & TreeMap

your Code Should be like that:

 SortedMap<String, String>   map = new TreeMap<>(new Comparator<String>() {
   @Override
   public int compare(String o1, String o2) {
   if(o1.length()==o2.length()&&o1.contains("_")&&o1.contains("_"))
  {
       String temp1,temp2;
   temp1=o1.substring(o1.lastIndexOf("_"));
    temp2=o2.substring(o2.lastIndexOf("_"));
    return temp1.compareTo(temp2);
   }
   else  if(o1.length()>o2.length())
  {

    return 1;
   }
   else  if(o1.length()<o2.length())
  {

    return -1;
   }
    return o1.compareTo(o2);
   }
 });

 map.put("100_101","lll");
 map.put("100_102","lll");
 map.put("100_101_103","lll");
 map.put("100_101_104","lll");
 map.put("100","lll");

 System.out.println(map);

see Java tutorial page for SortedMap.

Answer 4

Here try this as I can see you want to sort based on last Integer of the String ie for 100_101 you want to sort based on 101 . You need to implement comparator to satisfy this. Here's the code:

public class Main {

    public static void main(String a[]) {
        TreeMap<String, String> map = new TreeMap<String, String>(new CustomComparator());
        map.put("100_101", "lll");
        map.put("100_103", "lll");
        map.put("100_101_102", "lll");
        map.put("100_101_104", "lll");
        map.put("100", "lll");
        System.out.println(map);
    }
}

class CustomComparator implements Comparator<String> {

    @Override
    public int compare(String str1, String str2) {
        int a, b;
//Used this because your key may or may not contain "_"
        if (str1.contains("_")) {
            a = Integer.parseInt(str1.substring(str1.lastIndexOf('_') + 1));
        } else {
            a = Integer.parseInt(str1);
        }
        if (str2.contains("_")) {
            b = Integer.parseInt(str2.substring(str2.lastIndexOf('_') + 1));
        } else {
            b = Integer.parseInt(str2);
        }
//        System.out.println(Integer.parseInt(str1.substring(str1.lastIndexOf('_')+1))+"---"+Integer.parseInt(str2.substring(str2.lastIndexOf('_')+1)));
        return String.valueOf(a).compareTo(String.valueOf(b));
    }

}