How to iterate through Nested Map and Multiset? - Java/Guava

问题

How should I iterate through a Nested Map with such declaration?

• Map<String, Multiset<String>>

Please suggest if there are other hashmap/list that are more effective way of doing this hash population task?

import com.google.common.collect.Multiset;
import com.google.common.collect.TreeMultiset;

String[] foobarness = {"foo" , "bar", "ness", "foo", 
    "bar", "foo", "ness", "bar", "foo", "ness", "foo", 
    "bar", "foo", "ness", "bar", "ness", "foo", "bar", 
    "foo", "ness"};
String[] types = {"type::1", "type::2", "type::3", 
    "type::4",};

Map<String, Multiset<String>> typeTextCount = 
new HashMap<String, Multiset<String>>();

Multiset<String> textAndCount 
    = TreeMultiset.create();

for (int i=0; i<types.length; i++) {
    // I know it's kinda weird but in my task, 
    //  i want to keep adding only 1 to the count for each entry.
    // Please suggest if there is a better hashmap/list for such task.
    if ((types[i]== "type::1") or (types[i]== "type::3")) {
        for (String text : foobarness) {
            // I don't worry too much about how i 
            //  populate the Map, it is iterating through 
            //  the Map that I have problem with.           
            textAndCount.put(text, 1); 
        }
    }

    if ((types[i]== "type::2") or (types[i]== "type::4")) {
        for (String text : foobarness) 
            textAndCount.put(text, 1);
    }
}

So now the hashmap is populated, how do i iterate through that complex nested map? I've tried the code below but I only got the 1st getValue() from my Multiset:

Iterator<Entry<String, Multiset<String>>> itTTC = 
    typeTextCount.entrySet().iterator();
while (itTTC.hasNext()) {
    Map.Entry textCt = (Map.Entry)itTTC.next();
    System.out.println(textCt.getKey() + " :\t" + textCt.getValue());
    itTTC.remove();
}

回答1:

In your code you aren't adding your Multiset to your Map. That's why you are not seeing any output.

In your code I did this:

typeTextCount.put(types[i], textAndCount);

inside the loop, and then with the same iterator I can see all the outputs like this :

type::3 :   [bar x 24, foo x 32, ness x 24]
type::2 :   [bar x 24, foo x 32, ness x 24]
type::4 :   [bar x 24, foo x 32, ness x 24]
type::1 :   [bar x 24, foo x 32, ness x 24]

EDIT: Complete code for reference:

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

import com.google.common.collect.Multiset;
import com.google.common.collect.TreeMultiset;

public class TestIterator {

    private static String[] foobarness  =
                                   {
            "foo", "bar", "ness", "foo", "bar", "foo", "ness", "bar", "foo", "ness", "foo", "bar", "foo", "ness",
            "bar", "ness", "foo", "bar", "foo", "ness"
                                   };
    private static String[] types      =
                                   {
            "type::1", "type::2", "type::3", "type::4",
                                   };
    public static void main(String[] args) {
        Map<String, Multiset<String>> typeTextCount = new HashMap<String, Multiset<String>>();

        Multiset<String> textAndCount = TreeMultiset.create();

        for (int i = 0; i < types.length; i++) {
            // I know it's kinda weird but in my task,
            // I want to keep adding only 1 to the count for each entry.
            // Please suggest if there is a better hashmap/list for such task.
            if (("type::1".equals(types[i])) || ("type::3".equals(types[i]))) {
                for (String text : foobarness) {
                    // I don't worry too much about how i
                    // populate the Map, it is iterating through
                    // the Map that I have problem with.
                    textAndCount.add(text, 1);
                }
            }

            if (("type::2".equals(types[i])) || ("type::4".equals(types[i]))) {
                for (String text : foobarness)
                    textAndCount.add(text, 1);
            }
            typeTextCount.put(types[i], textAndCount);
        }

        Iterator<Entry<String, Multiset<String>>> itTTC = typeTextCount.entrySet().iterator();
        while (itTTC.hasNext()) {
            Map.Entry textCt = (Map.Entry) itTTC.next();
            System.out.println(textCt.getKey() + " :\t" + textCt.getValue());
            itTTC.remove();
        }
    }
}

来源：https://stackoverflow.com/questions/8522268/how-to-iterate-through-nested-map-and-multiset-java-guava