Get value of HashMap within TreeMap

Question

I've got a TreeMap that stores a HashMap inside of it. I feel like I should be able to find this, but I just can't seem to find it on Google.

I've got a TreeMap with a HashMap stored inside of it, I iterate over it like so:

                    while (i.hasNext()) {
                        Map.Entry me = (Map.Entry) i.next();
                        System.out.print(me.getKey() + ": ");
                        System.out.println(me.getValue());
                    }

That will print out an output (example line):

I/System.out﹕ 32: {walks=32, pic=http://****/images/walkers/chase.png, name=Chase, dist=6096.8589024135445}

I'm wondering how to now grab pic, name, dist from this HashMap.

Edit: I'm not understanding where people missed the point. I put a HashMap into the TreeMap. Inside of the TreeMap is a HashMap. I guess I can show you what a HashMap is, but you guys know that already!

TreeMap dist_mp=new TreeMap();
Map<String, String> mp1 = new HashMap<String,String>();
mp1.put("dist", distanceInMiles + "");
mp1.put("name", obj.getString("first_name"));
mp1.put("pic", obj.getString("pic"));
mp1.put("walks", obj.getString("walks"));
dist_mp.put(distanceInMiles, mp1);

atleast show how you are putting data into `HashMap`, what object you are adding — Ankur Singhal, Jan 20 '15 at 03:01
Added more, I'm new to Java so I thought it was obvious, my bad! — user1610719, Jan 20 '15 at 03:07
posted with output, what you did was correct, just missed second iteration for hashmap, removed my downvote — Ankur Singhal, Jan 20 '15 at 03:16
Voting to close as unreproducible. Please provide a complete example with a full error message. — Sotirios Delimanolis, Jan 20 '15 at 03:27
@SotiriosDelimanolis Who said there was an error? He's simply getting the `toString`ed version (`toStrung`?) of the inner map, instead of pulling out its values. — Dawood ibn Kareem, Jan 20 '15 at 03:31
@DavidWallace They seem to know that `put` exists. I will assume they know `get` exists, but they keep insisting it doesn't because of whatever errors. I'm waiting for those clarifications. — Sotirios Delimanolis, Jan 20 '15 at 03:36
I presume they just mean it's not showing up in their autocomplete list, because `me` doesn't have any type parameters, so `me.getValue()` is `Object` instead of `HashMap`. @SotiriosDelimanolis — Dawood ibn Kareem, Jan 20 '15 at 03:50
@DavidWallace Then it should be closed as a duplicate of [this canonical answer](http://stackoverflow.com/questions/2770321/what-is-a-raw-type-and-why-shouldnt-we-use-it). — Sotirios Delimanolis, Jan 20 '15 at 03:52
@SotiriosDelimanolis I might agree if this question bore the slightest resemblance to that one. — Dawood ibn Kareem, Jan 20 '15 at 04:31

score 2 · Accepted Answer · answered Jan 20 '15 at 03:16

All you need is a cast to the TreeMap values to a Map again:

while (i.hasNext()) {
    Map.Entry me = (Map.Entry) i.next();
    System.out.print(me.getKey() + ": ");

    // Cast to a Map again
    Map<String, String> mp = (Map<String, String>) me.getValue();

    // get() works now
    System.out.print("name = " + mp.get("name"));
    System.out.print("pic = " + mp.get("pic"));
    System.out.println("dist = " + mp.get("dist"));
}

score 1 · Answer 2 · answered Jan 20 '15 at 03:15

Need to iterate twice, one for TreeMap and then for HashMap

 public static void main(String[] args) {
        TreeMap<String, Map<String, String>> dist_mp = new TreeMap<String, Map<String, String>>();
        Map<String, String> mp1 = new HashMap<String, String>();
        mp1.put("dist", "6096.8589024135445");
        mp1.put("name", "Chase");
        mp1.put("pic", "http://****/images/walkers/chase.png");
        mp1.put("walks", "32");
        dist_mp.put("32", mp1);

        for (Map.Entry<String, Map<String, String>> entry : dist_mp.entrySet()) {
            String key = entry.getKey();
            System.out.println(key);
            Map<String, String> myMap = entry.getValue();

            for (Map.Entry<String, String> entry1 : myMap.entrySet()) {
                System.out.println(entry1.getKey() + " => " + entry1.getValue());
            }
        }
    }

output

32
walks => 32
name => Chase
pic => http://****/images/walkers/chase.png
dist => 6096.8589024135445

score 0 · Answer 3 · answered Jan 20 '15 at 02:59

0

Your HashMap seems to be holding an object of some class, which is depicted here:

{walks=32, pic=http://****/images/walkers/chase.png, name=Chase, dist=6096.8589024135445}

Identify the class, and if getter methods are available for pic, name, dist, then use them.

answered Jan 20 '15 at 02:59

Juned Ahsan

67,789
12
98
136

Yea I don't see any getter methods. I'm thinking I'll have to change the object into something else, as it seems the HashMap didn't stay a HashMap – user1610719 Jan 20 '15 at 03:09

score 0 · Answer 4 · answered Jan 20 '15 at 03:01

0

I think you are just asking how to get the value associated with a key:

map.get("pic");

answered Jan 20 '15 at 03:01

sprinter

27,148
6
47
78

It won't let me use get. I added more details about the makeup of the TreeMap, to show the HashMap I mentioned I was adding to it. – user1610719 Jan 20 '15 at 03:10

Dawood ibn Kareem · Answer 5 · 2015-01-20T03:26:04.700

-1

You want me.getValue().get("pic"), me.getValue().get("name") and me.getValue().get("dist").

This assumes that you're using generics, that your TreeMap is declared as a Map<Integer, HashMap<String, String>> and that your Map.Entry that you iterate with is declared as a Map.Entry<Integer, HashMap<String, String>>.

Also, you could iterate more easily with a for-each loop.

Map<Integer, HashMap<String, String>> theTreeMap = new TreeMap<>();

// Populate the map here.

for (Map.Entry<Integer, HashMap<String, String>> me : theTreeMap.entrySet()) {
    System.out.println(me.getValue().get("pic"));
    System.out.println(me.getValue().get("name"));
    System.out.println(me.getValue().get("dist"));
}

edited Jan 20 '15 at 03:26

answered Jan 20 '15 at 03:04

Dawood ibn Kareem

77,785
15
98
110

get isn't available, I added more details! – user1610719 Jan 20 '15 at 03:09
What do you mean "get isn't available"? You said it was a `HashMap`. You ARE using generics, right, so that you don't have to cast it? Something like `TreeMap>` or whatever the types are meant to be? – Dawood ibn Kareem Jan 20 '15 at 03:10
Check my edit. That being said, I added TreeMap walks_mp = new TreeMap>(); as the constructor and it still doesn't let me use the code you suggested. get isn't there – user1610719 Jan 20 '15 at 03:16
What doesn't let you? `HashMap` has a method called `get`. – Dawood ibn Kareem Jan 20 '15 at 03:16
It says "Cannot resolve method get()" when I try to use me.getValue().get("dist"). It's likely something else I did, but it isn't there. If I do me.getValue().getClass(), I get class java.util.HashMap – user1610719 Jan 20 '15 at 03:18
And `me` is declared as `Map.Entry>` to match the declaration of your `TreeMap`? – Dawood ibn Kareem Jan 20 '15 at 03:19

Get value of HashMap within TreeMap

5 Answers5