I have a project where I save some data coming from different channels of a Soap Service, for example:
String_Value Long_timestamp Double_value String_value String_value Int_value
I can have many lines (i.e. 200), with different values, like the one above.
I thought that I could use an ArrayList, however data can have a different structure than the one above, so an ArrayList maybe isn't a good solution in order to retrieve data from it.
For example above I have, after the first two values that are always fixed, 4 values, but in another channel I may have 3, or 5, values. What I want retrieve data, I must know how many values have a particular line, and I think that Arraylist doesn't help me.
What solution could I use?
When you have a need to uniquely identify varying length input, a HashMap usually works quite well. For example, you can have a class:
public class Record
{
private HashMap<String, String> values;
public Record()
{
// create your hashmap.
values = new HashMap<String, String>();
}
public String getData(String key)
{
return values.get(key);
}
public void addData(String key, String value)
{
values.put(key, value);
}
}
With this type of structure, you can save as many different values as you want. What I would do is loop through each value passed from Soap and simply add to the Record, then keep a list of Record objects.
Record rec = new Record();
rec.addData("timestamp", timestamp);
rec.addData("Value", value);
rec.addData("Plans for world domination", dominationPlans);
You could build your classes representing the entities and then build a parser ... If it isn't in a standard format (eg JSON, YAML, ecc...) you have no choice to develop your own parser .
Create a class with fields.
class ClassName{
int numberOfValues;
String dataString;
...
}
Now create an ArrayList of that class like ArrayList<ClassName> and for each record fill that class object with numberOfValues and dataString and add in Arraylist.
Related
I am trying to serialize Observable Maps with an Serialiazation Proxy.
These two properties need to be saved.
private final MapProperty<Integer, Cargo> allCargoStoredMap;
private final MapProperty<Cargo, CargoLogisticData> cargoLogisticDataMap;
I thought i can save the values in an array like this:
this.cargoLogisticDataAsArray = warehouseManagement.getCargoCargoLogisticDataMap().values().toArray(new CargoLogisticData[0]);
this.cargoAsArray = warehouseManagement.getAllCargoStoredMapProperty().values().toArray(new Cargo[0]);
Then i want to pass i to an Constructor, and rebuild the properties.
public Constructor (List<Cargor> cargos, List<CargoLogisticData>) {
ObservableMap<Integer, Cargo> cargos = FXCollections.observableHashMap();
//How do i add my cargos to a map?
this.allCargoStoredMap = new SimpleMapProperty<>(cargos);
}
Any Idea how i can add the the List Entrys to my map?
I thought i maybe have to save 4 Arrays. Two with key, two with values. And then add those again.
Any Ideas ?
This can be a simple solution if I don't get it wrong
allCargoStoredMap.values().stream().forEach(cargo -> {
CargoLogisticData logisticsData=cargoLogisticDataMap.get(cargo);
/*
You have cargo and related logistics data here.
You can create which data model you want to store and use it
*/
})
To update an object in Firebase, I'm using this code, that transforms my model into a dictionary.
This is the method that does such thing:
private static Map<String, Object> getPlayerData(Player player) {
Map<String, Object> data = new HashMap<>();
data.put(PLAYER_ID_KEY, player.getId());
data.put(PLAYER_NAME_KEY, player.getFullName());
data.put(PLAYER_SCORE_KEY, player.getScore());
data.put(PLAYER_STATUS_KEY, player.getStatus());
return data;
}
and this is how I use the result, setting it as a value for theFirebaseRef :
Map<String, Object> playerData = getPlayerData(userAsPlayer, newPlayerStatus);
theFirebaseRef.setValue(playerData, new Firebase.CompletionListener() {/**irrelevant code**/});
It works, but the PLAYER_SCORE_KEY ends up as a string in Firebase, when it should be an int:
I guess it makes sense because I'm doing a Map and declaring its values are of type Object.
Is there a way to make PLAYER_SCORE_KEY be an int when setting the value from a Map<String, Object>?
Edit:
The getter getScore() returns an int:
public int getScore() {
return score;
}
Edit:
To clarify, score is stored as a String only when called from my app. When either the web/iOS client add/modify a player, they save it as an int.
The problem is that Android is the only one not doing so!
(Setting my model as a value as done in the Firebase documentation isn't an option because the Firebase property names are ugly and the server guy uses different names for everything...)
I believe your problem is your map parameters. You probably will need to make two maps, one with parameters (String, Object) like you have, and another of type (Integer, Object) to hold any integer information. Then set the values in Firebase accordingly.
Otherwise, you might could use Integer.parseInt() on PLAYER_SCORE_KEY to convert it to an integer, then set this value in Firebase directly instead of passing it in the map.
I'm relatively new to Java and I have a question about what type of data structure would be best for my case. I have a set of data which are essentially key-value pairs, however each value may correspond to multiple keys and each key may correspond to multiple values. A simplified example would be:
Red-Apple
Green-Apple
Red-Strawberry
Green-Grapes
Purple-Grapes
Considering the above example, I need to be able to return what color apples I have and/or what red fruits I have. The actual data will generated dynamically based upon an input file where each set will be anywhere from 100-100,000 values and each value may correspond to hundreds of values in the other set.
What would be the most efficient way to store and parse this data? I would prefer a solution as native to java as possible rather than something such as an external database.
This question is related, but I'm not sure how to apply the solution in my case given that I would need to assign multiple values to each key in both directions.
As you can't have duplicate keys in a Map, you can rather create a Map<Key, List<Value>>, or if you can, use Guava's Multimap.
Multimap<String, String> multimap = ArrayListMultimap.create();
multimap.put("Red", "Apple");
multimap.put("Red", "Strawberry");
System.out.println(multimap.get("Red")); // Prints - [Apple, Strawberry]
But the problem is you can't ask for the keys of a given object, I'll keep looking and make and edit if I find something else, hope it helps.
Still, you can make the reverse yourself by iterating the map and finding the keys for the object.
I suggest you use Guava's Table structure. Use color as your row keys and fruit as your column key or the other way round. Specifically, HashBasedTable is well suited for your case.
As per your use case, you wouldn't need to store anything for the values. However, these Tables don't allow null values. You could use a dummy Boolean or any other statistical useful value, i.e. date and time of insertion, user, number of color/fruit pairs, etc.
Table has the methods you need, such as column() and row(). Bear in mind that the docs say that these structures are optimized for row access. This might be OK for you if you plan to access by one key more than by the other.
You can create your own custom data structure
public class MultiValueHashMap<K, V> {
private HashMap<K, ArrayList<V>> multivalueHashMap = new HashMap<K, ArrayList<V>>();
public static void main(String[] args) {
MultiValueHashMap<String, String> multivaluemap = new MultiValueHashMap<String, String>();
multivaluemap.put("Red", "Apple");
multivaluemap.put("Green", "Apple");
multivaluemap.put("Red", "Strawberry");
multivaluemap.put("Green", "Grapes");
multivaluemap.put("Purple", "Grapes");
for(String k : multivaluemap.keySet()){
System.out.println(k + " : " + multivaluemap.get(k).toString());
}
}
public void put(K key, V value){
if (multivalueHashMap.containsKey(key)){
ArrayList<V> values = multivalueHashMap.get(key);
values.add(value);
}else{
ArrayList<V> values = new ArrayList<V>();
values.add(value);
multivalueHashMap.put(key, values);
}
}
public Set<K> keySet(){
return multivalueHashMap.keySet();
}
public ArrayList<V> get(K key){
return multivalueHashMap.get(key);
}
}
The output should be
Red : [Apple, Strawberry]
Purple : [Grapes]
Green : [Apple, Grapes]
I am using a class where I am taking input as the file name and the file location. I have a pre defined file names, so I will match the predefined file names with the file name that I received and then store the values accordingly. Please look at the code below
//Set of storage maps and tables
public class storage
{
//Storage set
public static Set<Integer> tiger = new HashSet<Integer>();
//Storage set
public static Set<Integer> lion = new HashSet<Integer>();
//This is the table used for storing the browser customer count
public static Table<String,String,Integer> elephant = HashBasedTable.create();
//Storage map
public static Map<String, String> monkey = new HashMap<String, String>();
public static void storeDataDirector(String fileLocation,String fileName) throws Exception
{
if (fileName = monkey)
**update the "monkey map"**
}
This is my problem, also I have lot of maps and tables to be used so I wouldn't be able to use multiple if conditions and then check and update the same.
What I would like to know is the below
As I have said earlier, The file name that I am sending to the program which is "String filename" has the same name of the "Map monkey" but the former is a String and the latter is the map. I would like to know if I will be able to use the string variable as a reference to the map instance as both of them have the same name . This will highly avoid the if conditions that I am using in the program and thus I would like to possible solution for this ... Anything related to type caseting ort
You need to have another Map - whose key is a String and value is a Map. Something like Map<String,Map> allMaps = new HashMap<String,Map>()
Once you have this map , populate it with all your filenames and the corresponding maps monkey.
allMaps .put("monkey", monkey)
If a string filename corresponds to not a map but to a set , then you need to declare something more general Map<String,Object> allMaps = new HashMap<String,Object>(). Ofcourse this means you need to cast the value to its particular type before you can do any meaningful thing with it.
Then , to use this map , use your filename argument
Map monkeyAgain = allMaps.get(filename)
You can use reflection:
Storage.class.getField(fileName).get(null)
You will still have to cast the returned object. I do not think this the right approach.
The idea is to relate them in a Map, and use the file name as a key for example
Map<String, Map<String, String>>
// file store structure
If you need a generic solution, you could solve this by implementing an abstraction of your store structure, by implementing an interface similar to this one:
// T is the store type and U is the original type (String from file for instance...)
public interface StoreUnit<T, U> {
void update(U record);
List<T> list();
}
so you will have an implementation for each case (Set, Map, Table ...) and will relate it in a map using the file name as key.
monkeyFileName => MapStoreUnit<Entry<String,String>,String>
tigerFileName => SetStoreUnit<Integer, String>
elephantFileName => TableStoreUnit<Entry<Entry<String,String>,String>,String> // not sure if for Table there is something better than Entry ;)
When you wanna update some store you perform a get over the map using the file name as key, and invoking update method implemented with the record (that could be an String, complex Object) and so on. When you need to read something from there you could use the list method.
I have a java Set of Result objects. My Result class definition looks like this:
private String url;
private String title;
private Set<String> keywords;
I have stored my information in a database table called Keywords which looks like this
Keywords = [id, url, title, keyword, date-time]
As you can see there isn't a one-to-one mapping between an object and a row in the database. I am using SQL (MySQL DB) to extract the values and have a suitable ResultSet object.
How do I check whether the Set already contains a Result with a given URL.
If the set already contains a Result object with the current URL I simply want to add the extra keyword to the Set of keywords, otherwise I create a new Result object for adding to the Set of Result objects.
When you iterate over the JDBC resultSet (to create your own set of Results) why don't you put them into a Map? To create the Map after the fact:
Map<String, List<Result>> map = new HashMap<String, List<Result>>();
for (Result r : resultSet) {
if (map.containsKey(r.url)) {
map.get(r.url).add(r);
} else {
List<Result> list = new ArrayList<Result>();
list.add(r);
map.put(r.url, list);
}
}
Then just use map.containsKey(url) to check.
Normalization is your friend
http://en.wikipedia.org/wiki/Database_normalization
If it's possible, I suggest changing your database design to eliminate this problem. Your current design requries storing the id, url, title and date-time once per key word, which could waste quite a bit of space if you have lots of key words
I would suggest having two tables. Assuming that the id field is guarenteed to be unique, the first table would store the id, url, title and date-time and would only have one row per id. The second table would store the id and a key word. You would insert multiple rows into this table as required.
Is that possible / does that make sense?
You can use a Map with the URLs as the keys:
Map<String, Result> map = new HashMap<String, Result>();
for (Result r : results) {
if (map.containsKey(r.url)) {
map.get(r.url).keywords.addAll(r.keywords);
} else {
map.put(r.url, r);
}
}
I think that you need to make an override on equals() method of your Result class. In that method you will put your logic that will check what you are looking for.
N.B. You also need to know that overrideng the equals() method, you need to override also hashCode() method.
For more on "overriding equals() and hashCode() methods" topic you can look at the this another question.