hashmap

问题 I want to add the values of the same keys in a hashmap. For example: ABC --> 123 DEF --> 456 ABC --> 123 XXX --> 111 XXX --> 222 should become: ABC --> 246 DEF --> 456 XXX --> 333 Here's the code I have so far: public class Reading { @SuppressWarnings("unchecked") public static void main(String[] args) throws IOException { //Create hashmap to store the the string and int in the excel sheet HashMap<String, Integer> hm = new HashMap<String, Integer>(); String key = null; int value = Integer.MIN

问题 Still trying to learn maps and lists. My goal is to return a list from a nested list of maps. The function getMovements() works as expected. It renders a list of movements. Then I try to create another function getVariationsByMovement() which passes in the movement string name to attempt to return a list of variationNames. In my UI, I present a list of movements. The user selects a movements and the next page renders with a list of variations. I am stuck in the function below

问题 Still trying to learn maps and lists. My goal is to return a list from a nested list of maps. The function getMovements() works as expected. It renders a list of movements. Then I try to create another function getVariationsByMovement() which passes in the movement string name to attempt to return a list of variationNames. In my UI, I present a list of movements. The user selects a movements and the next page renders with a list of variations. I am stuck in the function below

问题 I have an hashmap of huge size (around 10^60). I am putting values in each entry one by one. Problem is to get the sum of values from hashmap for given range of keys. eg: Putting it in simple Hashmap has entries from 0 to 1000 as a key and every key has an value(BigInteger). Now problem is to get sum of values from range (say) 37 to 95. I have tried with iterator but when we go for huge map of size 10^60, it is time taking operation for large range of indices. I am trying it with streams but

问题 I have an hashmap of huge size (around 10^60). I am putting values in each entry one by one. Problem is to get the sum of values from hashmap for given range of keys. eg: Putting it in simple Hashmap has entries from 0 to 1000 as a key and every key has an value(BigInteger). Now problem is to get sum of values from range (say) 37 to 95. I have tried with iterator but when we go for huge map of size 10^60, it is time taking operation for large range of indices. I am trying it with streams but

问题 I would like to retrieve the original object of a key in a HashMap in Java, what is the best way to do it? For example HashMap<Integer, Integer> map = new HashMap<Integer, Integer>(); Integer keyObj = new Integer(10); Integer valueObj = new Integer(100); // And add maybe 1 million other key value pairs here //... later in the code, if I want to retrieve the valueObj, given the value of a key to be 10 Integer retrievedValueObj = map.get(10); //is there a way to retrieve the original keyObj

问题 How to filter a Map<String,Map<String,Employee>> using Java 8 Filter? I have to filter only when any of employee in the list having a field value Gender = "M". Input: Map<String,Map<String,Employee>> Output: Map<String,Map<String,Employee>> Filter criteria: Employee.genter = "M" Also i have to return empty map if the filtered result is empty. I tried the below, but it is not working as expected. It is returning the only if all the Employees are with gender "M". tempCollection.entrySet()

问题 I know how Hashmap works internally. Linkedhashmap is extending Hashmap class. So how Linkedhashmap is able to maintain the insertion order. I have read the javadoc for Linkedhashmap, but it does not have any details about this. Can somebody help me understand this? Thanks in advance. 回答1: http://docs.oracle.com/javase/7/docs/api/java/util/LinkedHashMap.html. Idea behind implementation is quite simple. It extends regular hashMap (so it has all hashMap goodies) but also builds double linked

问题 I know how Hashmap works internally. Linkedhashmap is extending Hashmap class. So how Linkedhashmap is able to maintain the insertion order. I have read the javadoc for Linkedhashmap, but it does not have any details about this. Can somebody help me understand this? Thanks in advance. 回答1: http://docs.oracle.com/javase/7/docs/api/java/util/LinkedHashMap.html. Idea behind implementation is quite simple. It extends regular hashMap (so it has all hashMap goodies) but also builds double linked

问题 In Clojure, how can I find the value of a key that may be deep in a nested map structure? For example: (def m {:a {:b "b" :c "c" :d {:e "e" :f "f"}}}) (find-nested m :f) => "f" 回答1: Clojure offers tree-seq to do a depth-first traversal of any value. This will simplify the logic needed to find your nested key: (defn find-nested [m k] (->> (tree-seq map? vals m) (filter map?) (some k))) (find-nested {:a {:b {:c 1}, :d 2}} :c) ;; => 1 Also, finding all matches becomes a matter of replacing some