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  • Dynamic object creation with HashMap

    - by Salor
    I want to use a HashMap to dynamically create objects based on the key. I have a Random Map Generator that stores the maps in 3D Arrays of Type Integer[][][]. Upon creation of the actual map I iterate through this array and based on the Integer I want to create the right block. Example: Integer[][][] map ... map[6][6][6] = 3; 3 is a Earth-Block and now I want to initialize a new Block of this type and give it the right coordinates. Currently I store my Bindings from Integer to Class in a HashMap(Integer, String) and create my objects like that: int id = array[x][y][z]; String block_name = Blocks.map.get(id); Block block = (Block) Class.forName(block_name).newInstance(); block.setPosition(x,y,z); But I want to avoid newInstance() if possible. I've never worked that dynamically with Java before and I couldn't find a solution like changing the HashMap to (Integer, Class) or something. I just need to create a new Object based upon the Integer. Any ideas/solutions? Thanks in advance and have a wonderful day!

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  • ANDROID : how to get value stored in ArrayList<HashMap<key,value>>?

    - by Roshni Kyada
    I have ArrayList. At another activity i want to access all values stored in ArrayList. I tried following code. ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>(); for(Hashmap<String, String> map: mylist) { for(Entry<String, String> mapEntry: map) { String key = mapEntry.getKey(); String value = mapEntry.getValue(); } } but it shows an error at for(Entry mapEntry: map) that it only interate over Array.

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  • Is it possible to use the values method for a HashMap if the values are ArrayLists?

    - by Denman
    I'm stuck trying to get something to work in an assignment. I have a HashMap<Integer, ArrayList<Object>> called sharedLocks and I want to check whether a certain value can be found in any ArrayList in the HashMap. The following code obviously wouldn't work because Object[] can't be cast to ArrayList[], but it is a demonstration of the general functionality that I want. ArrayList[] values = (ArrayList[]) sharedLocks.values().toArray(); boolean valueExists = false; for (int i = 0; i < values.length; i++) { if (values[i].contains(accessedObject)) { valueExists = true; } } Is there a way for me to check every ArrayList in the HashMap for a certain value? I'm not sure how to use the values method for HashMaps in this case. Any help would be much appreciated.

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  • Accessing nested HashMaps in Java

    - by mridang
    Hi, I have a HashMap in Java, the contents of which (as you all probably know) can be accessed by HashMap.get("keyname"); If a have a HashMap inside another HashMap i.e. a nested HashMap, how would i access the contents? Can i do this like this, inline: HashMap.get("keyname").get("nestedkeyname"); Thank you.

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  • Can a Java HashMap's size() be out of sync with its actual entries' size ?

    - by trix
    I have a Java HashMap called statusCountMap. Calling size() results in 30. But if I count the entries manually, it's 31 This is in one of my TestNG unit tests. These results below are from Eclipse's Display window (type code - highlight - hit Display Result of Evaluating Selected Text). statusCountMap.size() (int) 30 statusCountMap.keySet().size() (int) 30 statusCountMap.values().size() (int) 30 statusCountMap (java.util.HashMap) {40534-INACTIVE=2, 40526-INACTIVE=1, 40528-INACTIVE=1, 40492-INACTIVE=3, 40492-TOTAL=4, 40513-TOTAL=6, 40532-DRAFT=4, 40524-TOTAL=7, 40526-DRAFT=2, 40528-ACTIVE=1, 40524-DRAFT=2, 40515-ACTIVE=1, 40513-DRAFT=4, 40534-DRAFT=1, 40514-TOTAL=3, 40529-DRAFT=4, 40515-TOTAL=3, 40492-ACTIVE=1, 40528-TOTAL=4, 40514-DRAFT=2, 40526-TOTAL=3, 40524-INACTIVE=2, 40515-DRAFT=2, 40514-ACTIVE=1, 40534-TOTAL=3, 40513-ACTIVE=2, 40528-DRAFT=2, 40532-TOTAL=4, 40524-ACTIVE=3, 40529-ACTIVE=1, 40529-TOTAL=5} statusCountMap.entrySet().size() (int) 30 What gives ? Anyone has experienced this ? I'm pretty sure statusCountMap is not being modified at this point. There are 2 methods (lets call them methodA and methodB) that modify statusCountMap concurrently, by repeatedly calling incrementCountInMap. private void incrementCountInMap(Map map, Long id, String qualifier) { String key = id + "-" + qualifier; if (map.get(key) == null) { map.put(key, 0); } synchronized (map) { map.put(key, map.get(key).intValue() + 1); } } methodD is where I'm getting the issue. methodD has a TestNG @dependsOnMethods = { "methodA", "methodB" } so when methodD is executing, statusCountMap is pretty much static already. I'm mentioning this because it might be a bug in TestNG. I'm using Sun JDK 1.6.0_24. TestNG is testng-5.9-jdk15.jar Hmmm ... after rereading my post, could it be because of concurrent execution of outside-of-synchronized-block map.get(key) == null & map.put(key,0) that's causing this issue ?

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  • Mapping Hashmap of Coordinates in Hibernate with Annotation

    - by paddydub
    I've just started using hibernate and I'm trying to map walking distance between two coordinates into a hashmap, There can be many connections from one "FromCoordinate" to another "ToCoordinate". I'm not sure if i've implemented this correctly, What annotations do i need to map this MashMap? Thanks HashMap coordWalkingConnections = new HashMap(); @Entity @Table(name = "COORDCONNECTIONS") public class CoordinateConnection implements Serializable{ private static final long serialVersionUID = -1624745319005591573L; /** auto increasing id number */ @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "ID") @id private int id; @Embedded public FromCoordinate fromCoord; @Embedded public ToCoordinate toCoord; HashMap<FromCoordinate, ArrayList<ToCoordinate >> coordWalkingConnections = new HashMap<FromCoordinate, ArrayList<ToCoordinate >>(); } public class FromCoordinate implements ICoordinate { @Column(name = "FROM_LAT") private double latitude; @Column(name = "FROM_LNG") private double longitude; } public class ToCoordinate implements ICoordinate { @Column(name = "TO_LAT") private double latitude; @Column(name = "TO_LNG") private double longitude; @Column(name = "DISTANCE") private double distance; } DATABASE STRUCTURE id FROM_LAT FROM_LNG TO_LAT TO_LNG Dist 1 43.352669 -6.264341 43.350012 -6.260653 0.38 2 43.352669 -6.264341 43.352669 -6.264341 0.00 3 46.352669 -6.264341 43.353373 -6.262013 0.17 4 47.352465 -6.265865 43.351290 -6.261200 0.25 5 45.452578 -6.265768 43.352788 -6.264396 0.01 6 45.452578 -6.265768 45.782788 -6.234523 0.01 ..... ... . Example HashMap for HashMap<Coordinate, ArrayList<Coordinate>> <KEY{43.352669 -6.264341}, Arraylist VALUES{(43.350012,-6.260653,0.383657), (43.352669, -6.264341, 0.000095), (43.353373, -6.262013, 0.173201)}> <KEY{47.352465 -6.265865}, Arraylist VALUES{(43.351290,-6.261200,0.258781)}> <KEY{45.452578 -6.265768}, Arraylist VALUES{(43.352788,-6.264396,0.013726),(45.782788,-6.234523,0.017726)}>

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  • HashMap Memory Leak because of Dynamic Array

    - by Jake M
    I am attempting to create my own HashMap to understand how they work. I am using an array of Linked Lists to store the values(strings) in my hashmap. I am creating the array like this: Node** list; Instead of this: Node* list[nSize]; This is so the array can be any size at runtime. But I think I am getting a memory leak because of how I am doing this. I dont know where the error is but when I run the following simple code the .exe crashes. Why is my application crashing and how can I fix it? Note: I am aware that using a vector would be much better than an array but this is just for learning and I want to challenge myself to create the hashmap using a 'Dynamic' Array. PS: is that the correct term(Dynamic Array) for the kind of array I am using? struct Node { // to implement }; class HashMap { public: HashMap(int dynSize) { *list = new Node[dynSize]; size = dynSize; for (int i=0; i<size; i++) list[i] = NULL; cout << "END\n"; } ~HashMap() { for (int i=0; i<size; i++) delete list[i]; } private: Node** list; // I could use a vector here but I am experimenting with a pointer to an array(pointer), also its more elegant int size; }; int main() { // When I run this application it crashes. Where is my memory leak? HashMap h(5); system("PAUSE"); return 0; }

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  • When to trash hashmap contents to avoid performance degradation?

    - by Jack
    Hello, I'm woking on Java with a large (millions) hashmap that is actually built with a capacity of 10.000.000 and a load factor of .75 and it's used to cache some values since cached values become useless with time (not accessed anymore) but I can't remove useless ones while on the way I would like to entirely empty the cache when its performance starts to degrade. How can I decide when it's good to do it? For example, with 10 millions capacity and .75 should I empty it when it reaches 7.5 millions of elements? Because I tried various threshold values but I would like to have an analytic one. I've already tested the fact that emping it when it's quite full is a boost for perfomance (first 2-3 algorithm iterations after the wipe just fill it back, then it starts running faster than before the wipe) Thanks

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  • Transferring HashMap between client and server using Sockets (JAVA)

    - by sar
    I am working on a JAVA project in which there are multiple terminals. These terminals act as client and servers. For example if there are 3 terminals A,B and C.Then at any given point in time one of them say A, will be a client making broadcast request. The other two terminals, B and C, will reply. I am using sockets to make them communicate. Once the reply is received from all the other terminals A will check the pool of channels to see if any one of the channel is free. It takes up the free channel and making it availabilty false. The channelpool is implemented using HashMAp: HashMap channelpool = new HashMap(); channelpool = 1=true, 2=true, 3=false, 4=true, 5=true, 6=true, 7=true, 8=true, 9=true, 10=true So initially all the channels are true, any terminal can take any channel. But once the channel is taken it is set to false for the period of use and then reset to true. Now this Hashmap has to be shared among the distributed terminals. Also it should be kept up to date. I can not used a shared resource among the terminals to store the HashMap.Can someone tell me an easy way to transfer the HashMap between the terminals. I will appreciate if someone could point me to a website which discusses this.

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  • Beginnerquestion: How to count amount of each number drawn in a Lottery and output it in a list?

    - by elementz
    I am writing this little Lottery application. Now the plan is, to count how often each number has been drawn during each iteration of the Lottery, and store this somewhere. My guess is that I would need to use a HashMap, that has 6 keys and increments the value by one everytime the respective keys number is drawn. But how would I accomplish this? My code so far: public void numberCreator() { // creating and initializing a Random generator Random rand = new Random(); // A HashMap to store the numbers picked. HashMap hashMap = new HashMap(); // A TreeMap to sort the numbers picked. TreeMap treeMap = new TreeMap(); // creating an ArrayList which will store the pool of availbale Numbers List<Integer>numPool = new ArrayList<Integer>(); for (int i=1; i<50; i++){ // add the available Numbers to the pool numPool.add(i); hashMap.put(nums[i], 0); } // array to store the lotto numbers int [] nums = new int [6]; for (int i =0; i < nums.length; i++){ int numPoolIndex = rand.nextInt(numPool.size()); nums[i] = numPool.get(numPoolIndex); // check how often a number has been called and store the new amount in the Map int counter = hashMap.get numPool.remove(numPoolIndex); } System.out.println(Arrays.toString(nums)); } Maybe someone can tell me if I have the right idea, or even how I would implement the map properly?

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  • How to do an array of hashmaps?

    - by Joren
    This is what I tried to do, but it gives me a warning: HashMap<String, String>[] responseArray = new HashMap[games.size()]; "Type safety: The expression of type HashMap[] needs unchecked conversion to conform to HashMap[]"

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  • How to make a loop over all keys of a HashMap?

    - by Roman
    I try to do it in the following way: public String getValue(String service, String parameter) { String inputKey = service + ":" + parameter; Set keys = name2value.keySet(); Iterator itr = keys.iterator(); while (itr.hasNext()) { if (inputKey.equal(itr.next())) { return name2value.get(inputKey); } return ""; } } And I get an error message: cannot find symbol method.equal(java.lang.Object). I think it is because itr.next() is not considered as a string. How can I solve this problem? I tried to replace Set keys by Set<String> keys. It did not help.

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  • Dictionary/Hashmap......... what on earth is happening?

    - by Tom
    else if (!registryData.ContainsKey(kyInvolved)) { keyInvolved = new RegistryKy(kyInvolved); lock (registryDataLock) { registryData.Add(kyInvolved, keyInvolved); } processInvolved = new Proces(procInvolved); keyInvolved.addProcessToDict(processInvolved); } kyInvolved is a String which represents a registry key. keyInvolved is the actual registry key object. I'm being told that im adding a key which already exists, yet i have already checked to see whether it is in there or not???

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  • Java HashMap with Int Array

    - by Sunil
    Hello I am using this code to check that array is present in the HashMap. public class Test { public static void main(String[]arg) { HashMap<int[],String> map= new HashMap<int[],String>(); map.put(new int[]{1,2}, "sun"); System.out.println(map.containsKey((new int[]{1,2}))); } } But this prints False. How can I check that array is present in the HashMap. Thanks in advance.

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  • Iterating over hashmap injsp in struts application

    - by Rozer
    I have a Hashmap object that i am getting on a jsp page. HashMap<Integer,Gift_product> gift_hm = new HashMap<Integer,Gift_product>(); gift_hm.put(17,new Gift_product("doll",67)); now i need to iterate this and display content on jsp. as Gift_product class contains two fields name and price jsp output should be serial no. product name price 17 Doll 67 How can i achieve it..

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  • hashmap and list compare

    - by sarah
    Hi, I have a hashmap having four values a,b,c,d and list having only a i want to see if the hashmap has the value a and print it. hashmap.get('data') results a,b,c,d list l is having a how will i print only the value a

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  • How to use Map element as text of a JComboBox

    - by llm
    I am populating a JComboBox (using addItem()) with all the elements of a collection. Each element in the collection is a HashMap (so its a ComboBox of Hashmaps..). My question is - Given that I need each item to be a HashMap how do I set the text to apear in the combobox on the GUI? It needs to be the value of a certain key in the map. Normally if I am populating a combobox with my own type, I would just overide the toString() method...but I am not sure how to acheive this since I am using a Java HashMap. Any ideas (if possible, without implementing my own HashMap)? Update: It seems like there isn't anyway to avoid having the object int the JComboBox overide toString() if I want custom functionality..I wish there was a way to (1) specify the objects to be loaded into the JComboBox and (2) specify how these objects are to appear in the GUI.

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  • XMLAdapter for HashMap

    - by denniss
    I want to convert a list of items inside of my payaload and convert them into a hashmap. Basically, what I have is an Item xml representation which have a list of ItemID. Each ItemID has an idType in it. However, inside my Item class, i want these ItemIDs to be represented as a Map. HashMap<ItemIDType, ItemID> The incoming payload will represent this as a list <Item>... <ItemIDs> <ItemID type="external" id="XYZ"/> <ItemID type="internal" id="20011"/> </ItemIDs> </Item> but I want an adapter that will convert this into a HashMap "external" => "xyz" "internal" => "20011" I am right now using a LinkedList public class MapHashMapListAdapter extends XmlAdapter<LinkedList<ItemID>, Map<ItemIDType, ItemID>> { public LinkedList<ItemID> marshal(final Map<ItemIDType, ItemID> v) throws Exception { ... } public Map<ItemIDType, ItemID> unmarshal(final LinkedList<ItemID> v) throws Exception { ... } } but for some reason when my payload gets converted, it fails to convert the list into a hashmap. The incoming LinkedList of the method unmarshal is an empty list. Do you guys have any idea what I am doing wrong here? Do I need to create my own data type here to handle the LinkedList?

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  • Iterate over a list and put data in hashmap

    - by sarah
    I am having a list where i need to loop over it and put its data in hashmap,i am using this approach for(int i=0;i<list.size();i++) { HashMap hMap=new HashMap(); hMap.put("Data", list); } But when i need to read the value from hMap i am doing in this way Collection c = hMap.values(); Iterator itr = c.iterator(); while(itr.hasNext()) { System.out.println("next val is--"+itr.next()); } next vali is--- is printed in com.bean.xyz@23032bc[id=1] format ,i need the exact data,how will i do this ?

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  • Iterating over hashmap in JSP in struts application

    - by Rozer
    I have a HashMap object that I am getting on a JSP page. HashMap<Integer,Gift_product> gift_hm = new HashMap<Integer,Gift_product>(); gift_hm.put(17,new Gift_product("doll",67)); Now I need to iterate this and display content on JSP. The Gift_product class contains two fields: name and price. JSP output should be serial no. product name price 17 Doll 67 How can I achieve it?

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