keySet « HashMap « Java Collection Q&A

1. What is the time complexity of java.util.HashMap class' keySet() method?    stackoverflow.com

I am trying to implement a plane sweep algorithm and for this I need to know the complexity of java.util.HashMap class' keyset() method. What i feel, it would be O(n log n). ...

2. is the Java HashMap keySet() iteration order consistent?    stackoverflow.com

I understand that the Set returned from a Map's keySet() method does not guarantee any particular order. My question is, does it guarantee the same order over multiple iterations. For example

Map<K,V> ...

3. Using the keySet() method in HashMap    stackoverflow.com

I have a method that goes through the possible states in a board and stores them in a HashMap

void up(String str){
  int a = str.indexOf("0");
  if(a>2){
   String ...

4. Hashmap.keySet(), foreach, and remove    stackoverflow.com

I know that it's typically a big no-no to remove from a list using java's "foreach" and that one should use iterator.remove(). But is it safe to remove() if I'm ...

5. Java: problem with hashmap and keyset()    stackoverflow.com

Here's what I'm doing (it's my "homework"): the assignment is to make a map of gerbils and then flip through it using keySet() and get(key);

import java.util.*;

class Gerbil
    {
 ...

6. HashMap null keySet    stackoverflow.com

I am trying to loop over an HashMap with the keySet as below:

for (String key : bundle.keySet()) {
    String value = bundle.get(key);
    ...
}

7. How expensive is a call to java.util.HashMap.keySet()?    stackoverflow.com

I implemented a sparse matrix as List<Map<Integer,Double>>.
To get all entries of row i I call list.get(i).keySet(). How expensive is this call? I also used the trove library for an alternative ...

8. What causes the slightly unpredictable ordering of the iterator() for the java.util.HashSet and HashMap.keySet() classes?    stackoverflow.com

Six years ago, I burned several days trying to hunt down where my perfectly deterministic framework was responding randomly. After meticulously chasing the entire framework ensuring that it was all using ...

9. Java: HashMap claims it has key, but somehow hasn't    stackoverflow.com

I have a HashMap mapping objects of my Context class to Integers. In the Context class, I did override the public int hashCode() and public boolean equals(Object c) of java.lang.Object. However, ...

10. Casting HashMap.keySet()    coderanch.com

import java.util.*; class Counter { int i = 1; public String toString() { return Integer.toString(i); } } public class Statistics { public static void main(String[] args) { HashMap hm = new HashMap(); for(int i = 0; i < 10000; i++) { // Produce a number between 0 and 20: Integer r = new Integer((int)(Math.random() * 20)); if(hm.containsKey(r)) ((Counter)hm.get(r)).i++; else hm.put(r, new ...

11. HashMap.keySet()    coderanch.com

12. HashMap: keySet() and values order    coderanch.com

Hi Golem, The order of the elements would be same in the array. Just to clarify, if we have a hashmap with values (1, "one"), (2, "two"), (3, "three") keySet().toArray( new String[0] ) - would generate the keys of the elements in hashmap. - ["1","2","3"] values().toArray( new String[0] ) - would generate the values of the elements in hashmap.["one", "two", "three"] ...

13. Get values & keySet from an embedded HashMap    java-forums.org

import java.util.*; /** * Maintains a sorted list of accomodation requirements by town * @version 1.13.08.11 */ public class NationalRegister { private TreeMap allTowns; /** * Constructor for objects of class NationalRegister */ public NationalRegister() { super(); allTowns = new TreeMap(); } /** * Places a town and its requirements into the National Register */ public void addTown(Town town) ...