Hi folks, The h:selectBooleanCheckbox in question is in a h:dataTable (of Extras) within a h:dataTable (of Items) within a h:dataTable (of Categories). Many Items are displayed and each Item can have many Extras. <h:dataTable value="#{bean.categoryList}" var="category"> <h:column> <h:dataTable value="#{category.itemList}" v...
I have this HashMap that I need to print out in ascending order according to the values contained in it (not the keys). But the order when I print it out is seemingly random. What's the best way to print it out in ascending value order? Map<String, String> codes = new HashMap<String, String>(); codes.put("A1", "Aania"); codes.put("...
Hashtable does not allow null keys or values, while HashMap allows null values and 1 null key. Questions: Why is this so? How is it useful to have such a key and values in HashMap? ...
I want to serialize a hash map to a file and de-serialize it later on. #include <boost/serialization/hash_map.hpp> #include <boost/filesystem/fstream.hpp> #include <hash_map> class A: virtual public B { public: friend class boost::serialization::access; stdext::hash_map<std::string, myClass> myClassHashTable; template ...
Is checking for key existence in HashMap always necessary? I have a HashMap with say a 1000 entries and I am looking at improving the efficiency. If the HashMap is being accessed very frequently, then checking for the key existence at every access will lead to a large overhead. Instead if the key is not present and hence an exception oc...
Why doesn't that work in java, but this does Map<String, Map<String, Boolean>> myMap = new HashMap<String,Map<String,Boolean>>(); Just to clarify the below alteration of the nested HashMap shows a compiler error, whereas the above does not not; with a Map (not hashmap) Map<String, Map<String, Boolean>> myMap = new HashMap<String,Hash...
HashMap savedStuff = new HashMap(); savedStuff.put("symbol", this.symbol); //this is a string savedStuff.put("index", this.index); //this is an int gives me the warning: HashMap is a raw type. References to generic type HashMap<K,V> should be parameterized ...
HashMap myMap = (HashMap) getLastNonConfigurationInstance(); myMap is always null. getLastNonConfigurationInstance() returns an object. My map has two keys "symbol" and "name". public Object onRetainNonConfigurationInstance() { HashMap myMap = new HashMap(); myMap.put("symbol", this.symbol); final Object da...
I have a mutable HashMap and would like to use it like a default-dictionary. The obvious method appears to be to use getOrElse and provide the default value each time as a second value. However this seems a little inelegant in my use case since the default value doesn't change. var x = HashMap(1 -> "b", 2 -> "a", 3 -> "c") println(x.ge...
I wrote a hashmap in C# as a self study exercise. I wanted to implement chaining as a collision handling technique. At first I thought I'd simply use GetHashCode as my hashing algorithm, but I quickly found that use the numbers returned by GetHashCode would not always be viable (size of the int causes a out of mem if you want to index an...
I have a hashmap which contains items of struct Foo (not pointers). Now, I want to have pointers of those items in a list. How can I do this? I have tried to iterate the hashmap and insert the &*iter's to the list but the pointers get invalidated as soon as they are out of scope. I should be able to do this without dynamic allocation,...
I have a class which I want to set up as keys in HashMap. I already have implemented the compareTo method for that class. But still when I do: map.put(new MyKey(dummyArguements) , dummyValue ); System.out.println(map.get( new MyKey(dummyArguements) ) ); I get null. So that means hashmap is not able to identify that the two keys (for ...
I am wondering about the performance of Java HashMap vs JSONObject. It seems JSONObject stores data internally using HashMap. But JSONObject might have additional overhead compared to HashMap. Does any one know about the performance of Java JSONObject compared to HashMap? Thanks! ...
I have an array that looks something like this: [[100, "one"], [101, "one"], [102, "one"], [103, "two"], [104, "three"], [105, "three"]] What I would like to do is create an array of hashes that looks like this [{"one" => [100,101,102]}, {"two" => [103]}, {"three" => [104,105]}] The number portion will always be unique, the ...
This is my input data: [[:a 1 2] [:a 3 4] [:a 5 6] [:b \a \b] [:b \c \d] [:b \e \f]] I would like to map this into the following: {:a [[1 2] [3 4] [5 6]] :b [[\a \b] [\c \d] [\e \f]]} This is what I have so far: (defn- build-annotation-map [annotation & m] (let [gff (first annotation) remaining (rest annotation) seq...
I wrote a function very similar to this: def writeMyEl (x: TypeA, y: TypeB, z : TypeC) { if (myMutableHashMap.contains((x, y))) myMutableHashMap(x, y) = z else myMutableHashMap += (x, y) -> z } In real code Types A and B are enumerations ans C is a case class. myMutableHashMap is defined as a val of type scala.collectio...
Sorry in advance for the lengthy explanation! I have a C++ application that uses a hash_map to store a tree of information that was parsed from a text file. The values in the map are either a child hash_map or a string. These values were parsed from a text file and then stored into the map. I wanted to avoid having to send the strings ...
Hi, HashMap uses objects as a key. If you use int primitive as key, it uses auto boxing and create integer objects for key. is there any hashmap implementation uses primitive types as key. I dont want autoboxing. becuase hascode of integer is also value of integer. I am trying to create integer object pool. regards Trustin ...
Please refer to the code below. The keys "H_0000001" and "H_0000002" in the hashmaps HstTime and HstName get overwritten by other unique keys."H_000002" get overwritten by "H_00000010" and "H_0000001" gets overwritten by "H_00000012". package JavaTutes; import java.util.*; public class TCProcessData { String Unit1HST1ID = ...
Hello, I have a 2 enum values representing a mapping to object which I'm (currently) modeling with a HashMap with the 2 enums values are used as key and the object is the value. This is inefficient because what I'm doing is creating a new CompositeKey(Enum1 enum1, Enum2 enum2) for each combination of the Enum1.values() x Enum2.values()...