打印出包含另一个哈希图的哈希图

Question

I'm working on a program that takes in X amount of files and then uses multi-threading to count occurrences of words in each file it saves the result in a hash map.

Map<String, Map<String, Integer>>

I have a hash map like the above above in the format < file_Name < Word , occurrences > I want to export the entire map to a text file and save it.

Is there a simple solution to printing the entire map (order/sorting doesn't matter)?

Answer 1

If you want to do it yourself you can:

Map<String, Map<String, Integer>> dictionaries = null;

PrintWriter pw = null;

for(Map.Entry<String, Map<String, Integer>> dictionaryEntry : dictionaries.entrySet()) {

    for(Map.Entry<String, Integer>  wordCounts :  dictionaryEntry.getValue().entrySet()) {

        pw.print(dictionaryEntry.getKey() + ", " + wordCounts.getKey() + ", " + wordCounts.getValue());

    }

}

HashMap is Serializable so you could just use

ObjectOutputStream : http://docs.oracle.com/javase/7/docs/api/java/io/ObjectOutputStream.html

Answer 2

There are multiple ways to do this, of course. My favourite would be to use google-gson . It's a Java library to convert between JSON and Java objects. So, you will be able to retrieve the nested hash map structure with no trouble and no (well ... 1-2 lines) extra coding.

Here's a detailed gson example .

Answer 3

Here map contains filename --> another map

And m contains word-------> count

   Map<String, Map<String, Integer>> map = new HashMap<String, Map<String, Integer>>();
    Map<String, Integer> m = new HashMap<String, Integer>();
    m.put("abcd", 34);
    m.put("xyz", 34);
    map.put("a.txt", m);

    m=new HashMap<String, Integer>();
    m.put("abcd", 34);
    m.put("xyz", 34);
    map.put("b.txt", m);

    for(String s : map.keySet()){
        System.out.println("File name: "+s);
        Map<String, Integer> innerMap = map.get(s);
        for(String str:innerMap.keySet()){
            System.out.println(str+" : "+innerMap.get(str));
        }
        System.out.println("--------------------------------------------------------------------------------");
    }

output:

File name: b.txt
abcd : 34
xyz : 34
--------------------------------------------------------------------------------
File name: a.txt
abcd : 34
xyz : 34

Or Another way is simply you do like:

System.out.println(map);

Output:

{b.txt={abcd=34, xyz=34}, a.txt={abcd=34, xyz=34}}