如何对嵌套的哈希图进行排序？

Question

The hashmap below forms like a table with key-value pair strings. Integer represents row and column index respectively.

HashMap<Integer,HashMap<Integer,HashMap<String,String>>> fullMap = new HashMap<Integer,HashMap<Integer,HashMap<String,String>>>();

How do I sort the innermost hashMap? sort row by keys ascending order

unsorted output:

.      0           1           2   
0  john,men     ace,his    hish,opt  
1  vrix,alt    home,jul     ics,ard  

sorted output:

.      0           1           2   
0   ace,his     john,men    hish,opt 
1  home,jul      ics,ard    vrix,alt 

Answer 1

I recommend you sort your maps on use rather than change the way the data is stored.

If I understand your question, you wish to sort by the keys in the key-value pairs. If that is correct, then you can do:

void processRow(Map<Integer,Map<String,String>> row) {
    row.entrySet().stream().sorted(Map.Entry.comparingByKey())
        .forEach(entry -> ...);
}

As an aside, your analogy of your data structure as a table is confusing. It's a map from int to int to string to string. This could represent a table where each cell is a list of key/value pairs. But that's a pretty unusual table.

A more conventional representation of a relational table would be something like List<Map<Column,Value>> .

Answer 2

Sorting of map entries based on keys can be achieved using TreeMap. Create HashMap< Integer,TreeMap< String, String>> to maintain column format.

Map<Integer, Map<String,String>> map = new HashMap<>();
Map<String, String> treeMap1 = new TreeMap<>();
treeMap1.put("john","men");
treeMap1.put("ace","his");
treeMap1.put("hish", "opt");
Map<String, String> treeMap2 = new TreeMap<>();
treeMap2.put("vrix","alt");
treeMap2.put("home","jul");
treeMap2.put("ics", "ard");
map.put(1, treeMap1);
map.put(2, treeMap2);