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How can i convert Map of Strings and Object to a Map of Strings and List

I have method that should return Map<Strings, List<String>> but in the mean time my method gives me a Map<Strings, Object>, I want to transfer the values of object into a List of Strings.
Here is the current code:
#SuppressWarnings("unchecked")
static Map<String, List<String>> getQueryParameters(JsonObject inputJsonObject) {
JsonArray parameters = inputJsonObject.getJsonArray("parameters");
Optional<JsonObject> queryParameters = parameters.stream().
filter(JsonObject.class::isInstance).
map(JsonObject.class::cast).
filter(jsonObject -> jsonObject.getJsonObject("queryParameters") != null).
map(item -> item.getJsonObject("queryParameters")).findFirst();
Map<String, Object> paramMap = queryParameters.get().getMap();
paramMap contains key and value , values could be an arrays of integers
so I want to put them into the map below:
Map<String, List<String>> mystore = new LinkedHashMap<String, List<String>>();
My solution is this which did not work correctly
Map<String, List<String>> mystore = new LinkedHashMap<String, List<String>>();
Map<String, Object> paramMap = queryParameters.get().getMap();
Iterator it = paramMap.entrySet().iterator();
while (it.hasNext()) {
String key = it.next().toString();
if (!mystore.containsKey(key)) ;
mystore.put(key, new LinkedList<String>());
mystore.get(key).add(it.next().toString());
}
I was a key holding another key as value and is just a mix up , any suggestions?
After debuging what happens i see that mystore holds both "key and value" together as a key and value it hold the next "key and value as value

Should be something like this:
while (it.hasNext()) {
Map.Entry<String, Object> next = iterator.next();
String key = next.getKey();
Object value = next.getValue();
if (!mystore.containsKey(key)) mystore.put(key, new LinkedList<String>());
mystore.get(key).add(value.toString());
}

I'm not writing a program for you, but instead help you in finding a problem. You are confused with Entry. If you are using IDE, you should solve it easier. Look for this line :
String key = it.next().toString();
Entry has a K,V pair. The iterator returns an EntrySet and thus usage to get key is it.next().getKey() and it.next().getValue()
Now that you have a correct key, please go on debugging. Instead of putting and getting and manipulating in below lines of your code. Put with correct value instead?
Yours:
mystore.put(key, new LinkedList<String>());
mystore.get(key).add(it.next().toString());
What about?:
Entry entry = it.next();
//Get key and value here. DO coding using Entry's methods
List<String> ll = new LinkedList<String>();
ll.add(value)
mystore.put(key, ll);
Tip: Always have the Javadoc or reference documentation handy for knowing more. That's how you learn the language. Refer:https://docs.oracle.com/javase/7/docs/api/java/util/Map.Entry.html

Java How to access hash map data held in an array

learning Java and have figured out how to store a hashmap in an array. But I can't figure out how to get to the stored data. Here is a simplified version of what I'm doing. I've got as far as displaying the specific array items, but how do I access the hash map stored in the array?
import java.util.*;
public class HelloWorld {
public static void main(String[] args) {
Map<String, String> custOrder = new HashMap<String, String>();
List ordersPlaced = new ArrayList();
custOrder.put("colour", "blue");
custOrder.put("manu", "bmw");
custOrder.put("body", "4x4");
ordersPlaced.add(custOrder);
custOrder = new HashMap();
custOrder.put("colour", "green");
custOrder.put("manu", "merc");
custOrder.put("body", "saloon");
ordersPlaced.add(custOrder);
System.out.println(ordersPlaced.get(0).toString());
}
}
Hope that makes sense. Thanks in advance
Neil

You're already accessing it.
In order to get the iterate on the map's items, you can:
ordersPlaced.get(0).forEach((key, value) -> {
System.out.println("Key is: " + key + ", Value is: " + value);
});
Or, earlier to Java 8, something like:
for (Map.Entry<String, String> entry : ordersPlaced.get(0).entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
}
Please note that you should avoid using raw type list. Instead, you should have:
List<Map<String, String>> ordersPlaced = new ArrayList<>();
And then:
Map<String, String> m = ordersPlaced.get(0);

You know it already.
You can get back the stored map by writing
Map<String, String> placedCustOrder = ordersPlaced.get(0);
And avoid using raw types while using List. Declare your list as
List<Map<String, String>> ordersPlaced = new ArrayList<>();
I would like to know how to access the colour of the data stored in the array at location 0
Since you got the map as I said in the line 1
Map<String, String> placedCustOrder = ordersPlaced.get(0);
String colorVal = placedCustOrder.get("colour");
I strongly suggest you to look through Map documentation before proceeding further.

Hashmap value getting updated in all keys

I am having map like this
HashMap<String, List<String>> map = new HashMap<String, List<String>>();
map---> {A=[], B=[], C=[]}
I am trying to add "hai" to key A.
But it is getting added to all key. Below is my code
I am wrong somewhere
for (Entry<String, List<String>> entry : map.entrySet()) {
String a = entry.getKey();
if(a.equals(attr)){
List<String> temp = entry.getValue();
temp.add("hai");
map.put(a, temp);
System.out.println("----------"+map);
}
}
output: ------------{A=[hai], B=[hai], C=[hai]}
please suggest
Thanks in advance

Not sure why that's happening, maybe as Eran suggested it's in code you aren't showing. However, there's a much easier way to do this instead of iterating through all the keys...
Map<String, List<String>> map = new HashMap<>();
...
List<String> values = map.get(attr);
if(values == null) {
values = new ArrayList<String>();
map.put(attr, values);
}
values.add("hai");
And I'm just guessing here, but I suspect you are doing this to create the array in the first place...
Map<String, List<String>> map = new HashMap<>();
List<String> values = new ArrayList<>();
map.put("A", values);
map.put("B", values);
map.put("C", values);
This causes A, B, and C to all share the same instance of the List. Therefore when you manipulate the list under one key (say, A), you are really making the same change to the lists stored under all keys, because it is the SAME list for all three.
The fix for that is described above, but essentially you want to create a new instance of List for each key in the map.

You are probably putting the same List in all the values of the Map. However, that happens in code you didn't show. When you put a key in the Map for the first time, make sure you are creating a new List for its value.

Converting Each Value in static HashMap to String Java

I have got some troubles converting each value in my HashMap to a String.
private static HashMap<String, List<Music>> musiksammlung = new
HashMap<String, List<Music>>();
This is my constructor for the HashMap. The key represents the album, the value a list of tracks from this album.
Now I want to convert each Music object to a String without creating a new HashMap, is this
possible?
I've tried it with the Iterator scheme, for loop over the entry set and so on but nothing seems to work.
Edit://
My code for the convertmethod:
public HashMap<String, List<String>> generateFormatList() {
HashMap<String, List<String>> formatList = new HashMap<String, List<String>>();
for(String key : musiksammlung.keySet())
formatList.put(key, musiksammlung.get(key).toString());
return musiksammlung;
}
But this always results in an error "is not applicable for the Arguments (String, String) so I have no idea. Do I have to override toString()?

You're on the right path but you need to convert the existing List<Music> to a List<String> and put the List<String> into your new HashMap.
You also then want to return your newly created HashMap<String, List<String>> instead of your original one.
public HashMap<String, List<String>> generateFormatList() {
HashMap<String, List<String>> formatList = new HashMap<String, List<String>>();
for(String key : musiksammlung.keySet()) {
// Value to store in map
List<String> value = new ArrayList<String>();
// Get the List<Music>
List<Music> musicList = musiksammlung.get(key);
for (Music m: musicList) {
// Add String of each Music object to the List
value.add(m.toString);
}
// Add the value to your new map
formatList.put(key, value);
}
// Return the new map
return formatList;
}
So answer your question:
Now I want to convert each Music object to a String without creating a
new HashMap, is this possible?
You need to create a new HashMap, because it's storing different type of value: List<Music> is different from List<String>.
Also as mentioned in my previous answer, make sure you override Music.toString() so that it returns a meaningful String for you instead of the one it inherits from its parent classes, which includes at least java.lang.Object

formatList wants a List<String>, but musiksammlung.get(key).toString() returns a String (not a List<String>). Did you mean this?
HashMap<String, String> formatList = new HashMap<String, String>();

Have you tried something like this:
Iterator<String> it = musiksammlung.keySet().iterator();
while (it.hasNext()) {
List<Music> ml = musiksammlung.get(it.next());
for (Music m : ml)
System.out.println(m.toString());
}
And of course you should override the Music#toString() method with something you could use.

Try to change your HashMap like this:
private static HashMap<String, List<Object>> musiksammlung = new HashMap<String,List<Object>>();
So you can save any kind of objects in this HashMap. Also use instanceof to check the type of the object before using it.

Recursively Create Hasmaps in Java

I'm trying to create a new HashMap for each document I have as input. In pseudeocode I can think of something like:
For(eachInputDoc)
{
Map<String, String> mapInputNumber = new HashMap<String, String>;
}
So that for 4 documents you would have:
mapInput1
mapInput2
mapInput3
mapInput4
How can I accomplish this?

It looks like you're trying to declare variables dynamically. You can't do that in Java - the variables themselves are determined at compile time. However, you could create a list:
List<Map<String, String>> maps = new ArrayList<Map<String, String>>();
for (Document doc : docs)
{
Map<String, String> map = new HashMap<String, String>();
// Populate map from doc
maps.add(map);
}

I suggest you make an ArrayList of HashMaps.

You cannot dynamically generate names like mapInput1, mapInput2, etc in Java. You need to think of array or List. Also your problem is not recursive.

I'd do something like this:
Map<MyDocClass, Map<String, String>> myDocData = new HashMapMap<MyDocClass, Map<String, String>>();
for(MyDocClass doc : myDocs) {
Map<String, String> data = new HashMap<String, String>();
// populate the data
myDocData.put(doc, data);
}
Then you can easily access the data for each doc by doing
Map<String, String> data = myDocData.get(doc);

If you know/want to reference the name of the document, you could even use a HashMap of HashMaps.

I would have another map to hold the mapInputs something like this:
Map<Integer,Map<String,String>> context = new HashMap<Integer,Map<String,String>>();
for each(inputDoc)
{
Map<String, String> mapInput = new HashMap<String, String>();
context.put(index,mapInput);
}
U have the aproach of having a List(array,linked) instead of MAP, but this depends of how you`re gonna access that inputMaps! I would say that using a ArrayList is a good one too!

You need to put your hash maps into another (dynamic) container like ArrayList or other HashMap.