Difference Between Hashmap Linkedlist And Arraylist?
Jul 10, 2014What are the difference between hashmap, linkedlist and arraylist ... when they are used and why?
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Difference Between LinkedList And ArrayList
Feb 19, 2014I have just begin to understand collections in Java. I read about the differences between LinkedList and ArrayList but have several doubts on it. I have mentioned them below
1) Why retrieving in ArrayList is faster then LinkedList?. Since both have the get method how does performance differ?.
2) How does re-sizing happens internally in ArrayList when a item is added or removed?. How slow this is compared to the pointer re-shuffling in LinkedList when a item is added or removed?.
Will Initialization Of HashMap On Different Place Make Any Difference
Nov 21, 2014public class HashMapTest {
private static HashMap mp;
public static void main(String[] args) {
// TODO Auto-generated method stub
mp=new HashMap<String, String>();
}
}
This is My Code if I create Object in two place
1)Outside main() method but within class.
2)Inside main() method like above
Will these two approach makes any difference ?
I am asking a general senerio for creating any Type of Objects Primitives or References?
Which Is Efficient Arraylist Or Hashmap
Jan 30, 2014my project flow is html,css,js<--->ajax<-->jsp<--->jdbc(.java)<--->mysql. In that jdbc i am returning the records from the database and fill into the resultset. From the resultset i put all records in arraylist and passed to jsp then i am displaying data in the screen.Whether i can use arraylist, hashmap or treetable?
View Replies View RelatedUsing Arraylist Index And Items As Hashmap Key And Values?
Apr 6, 2014I am working on the Kevin Bacon - 6 degrees of bacon problem. I want to take my Array List and use the index and Values that I have saved in it as the Key and Value of a Hashmap. Below is my code.
HashMap<Integer, ArrayList<String>> actors =
new HashMap<Integer, ArrayList<String>>();
ArrayList array = new ArrayList();
try (BufferedReader br = new BufferedReader(
new FileReader("actors.txt"));)
[code]...
saving each one in it's own spot. I want to use the index of each one as the key to find it in the Hashmap....
JSF :: How To Convert Hashmap Values To Arraylist To Display On Page
Apr 2, 2015I need assigning the selected hashmap values into a list and to display the values in a jsf page. The user will select certificates and will be stored in the below list:
private List<String> selectedCertificates = new ArrayList<String>();
The selectedCertificates will have the values ("AA","BB"). Now I will be passing the list into a hashmap in order to get the names and to display them on the jsf page.
My code is below:
Map<String, String> CertificatesNames =
new HashMap<String,String>(selectedCertificates.size());
CertificatesNames.put("AA", "Certificate A");
CertificatesNames.put("BB", "Certificate B");
CertificatesNames.put("CC", "Certificate C");
for(String key1: selectedCertificates) {
System.out.println(CertificatesNames.get(key1));
}
I want to display in my jsf page :
Certificate A
Certificate B
Now my issue is that is how to display all the values of the CertificatesNames.get(key1) in the jsf page as I tried to do the below and it printed all the values when I used the #{mybean.beans} using the :
List beans =
new ArrayList(CertificatesNames.values());
So how to do this?
Difference Between ArrayList And Vector Class
Jun 26, 2014What is the difference between ArrayList and Vector class
View Replies View RelatedPopulating A LinkedList In Java?
Feb 17, 2014I have a LinkedList class that implements a game.
I want to create a list and populate it when a LinkedList object is created .
.
The game constructor takes a word.
How do you populate a LinkedList of any type for example suppose I have a LinkedList of the Integer type, How do I fill it up with 10 integers?
What Is The Starting Index Of LinkedList
May 12, 2014What is the starting index for linked list, 0 or 1. I know an array starts at 0 so wouldn't a linked list?
View Replies View RelatedLinkedList Remove Method
Apr 12, 2014My remove(item E) method is working fine if I remove an item that is in the list. However, it has an error when I try to remove an item which is not on the list!
Linked List Class
import java.util.NoSuchElementException;
public class LinkedList<E>
{
private Node<E> head; // head node of the list
private int size = 0; // number of elements that have been added to the list
// Returns the element at a specific list index.
// Big-O: O(n) (due to the nodeAt call, which must traverse the list)
public E get(int index)
[code]...
Searching For Object In LinkedList?
Nov 3, 2014I'm doing LinkedList at the moment and I'm having a bit of trouble with my assignment. The part I'm struggling with is remove an employee from a training course (as specified by their employee number),
what I'm confused about is iterating through the linked list to find the employee we're looking for. What I would do in this situation if I was using an array list is
for(Employee emp : myList) {
if(emp.getEmployeeNumber().equals(searchedNumber)) {
remove from training course..
break;
}
}
"Can only iterate over an array or an instance of java.lang.Iterable" is what it is telling me, and I can't figure out why/how its done differently for linked lists.
LinkedList No Such Method Error
Oct 27, 2014Okay, I'm having a problem with my LinkedList. When I run the driver program it's telling me that I have no "add" method and I don't know what's going on.
Driver Program:
public class TestLinkedList {
public static void main(String[] args)
{
MyLinkedList<String> L = new MyLinkedList<String>();
L.add("Browns");
L.add("Ravens");
L.add("Steelers");
[code]....
Getting NullExceptionPointer When Adding To LinkedList
Jul 20, 2014I can't figured out why it's keep giving me error when I tried to add i to the linkedlist. I tried changing it to other numbers but keep giving me nullExceptionPointer.
public static void subset(double[] weight, double[] value, int start) {
double sumWeights = 0;
for(int i = start; i<weight.length; i++){
if(sumWeights+weight[i]>L){
continue;
[Code] ....
Queue Class And Java LinkedList
Sep 30, 2014I have a Queue class (containing a LinkedList plus a few other variables and stats for my project), which works fine with the standard LinkedList, but I'm trying to add my own code for MyLinkedList.
However, I keep getting a NullPointerException at my remove method.
public class MyLinkedList<T> {
Node head;
public MyLinkedList() {
head = null;
}
public class Node {
T contents;
Node nextNode;
[Code] ......
Type Safety - Unchecked Cast From Object To LinkedList (EventData)
Feb 28, 2014I am getting "Type safety: Unchecked cast from Object to LinkedList<EventData>" in eclipse for a piece of code stated below
public LinkedList<EventData> loadFromFile(File file) {
queue=new LinkedList<EventData>();
//Some piece of code
return (LinkedList<EventData>)queue.clone(); //--->getting warning here
}
I know that because clone() method is returning Object, hence compiler doesn't have type information that's why showing warning. I don't want to suppress this warning instead i want to fix it.
Create Own ArrayList Using Collection Without Implementing ArrayList Itself
Feb 28, 2014I'm trying to create my own arraylist using Collection. My program doesn't do anything. Obviously, I haven't a clue.
import java.util.Collection;
import java.util.Iterator;
public class MyArrayList<T> implements java.util.Collection<T> {
private int size = 4;
private T[] mArray;
public MyArrayList(String[] args) {
[Code] ....
How To Get Value For Key In Hashmap
Sep 26, 2014In my code I read in a file of states and statecapitals then store them into a hashmap. I then ask the user what the capital is for the random state displayed.The problem I am having is getting the value for the random generated state. When I enter the correct capital for the state, it is still being marked incorrect. Here is my code.
Java Code: try {
Scanner scanner = new Scanner(file);
String[] values;
[code]....
Add Key-Value Of One HashMap As Value In Another HashMAp
Jul 30, 2014I have two Hasmaps as
Map<String,String> componentValueMap = new HashMap<String,String>();
Map<String,Map<String,String>> componentNameValueMap = new HashMap<String,Map<String,String>>();
I have for loop which are getting values from XML
XML structure as
<Raj>
<user>raj</user>
<password>123</password>
</Raj>
<Dazy>
<user>dazy</user>
<password>123</password>
</Dazy>
Now during first loop it will put user and password in map and after that put map refernce in another map. Same procedure for another values. But during iterating componentNameValueMap , i am getting Raj, Dazy as Key but not getting different values for them. I am getting latest values of Dazy in both Keys.
Because put method of Map<String,String> componentValueMap is replacing values. But I don't to replace them and want to get different values for different keys.
Getting Object From HashMap
Oct 23, 2014I am trying to retrieve a object from a hashMap not I am not sure what is wrong. I am trying to calculate if a car was speeding. They're 5 cameras and as they pass each camera I can calculate the speed. They key is camera number and I am sending in a Vehicle object.
Now I am trying to retrieve variables from the Vehicle so I can do the calculations. I am getting the error in the loop in void calculateSpeeding(). The loop is only for testing at the moment.
package online.practice.averageSpeed;
import java.util.Arrays;
import java.util.HashMap;
public class Vehicle {
String licensePlates;
[Code] ....
Printing A Key And A Value From HashMap
Mar 28, 2014I have a hashmap of the form HashMap <String, Set<String>>I am trying to create a method with one argument. The argument is a key for the hashmap, if it exists it should print out the key and the associated values. I'm falling over at even getting it to print the key, it keeps printing all the keys from within the hashmap as I don't know how to load the argument into it. I have this so far
Java Code:
public void printValue(String club)
{
boolean result = clubMap.containsKey(club);
if (result)
{
String key = clubMap.keySet(club).toString();
System.out.println(key );
[code]....
How To Find Particular Objects In HashMap
Dec 25, 2014Suppose i have a hashMap which includes instances of class Employees and instances of class Customers.
How can i get the employees objects only?
And would it be possible to find the oldest staff by comparing the ages stored in the age fields of the staff objects.
HashMap / How To Get Size Of Value And NOT The Keys
Apr 5, 2014I am asked in my assignment to make a program that accepts a text file as an example a novel and i have to sort each word as a PERSON or ORGANIZATION or LOCATION or O as in Other , example :
Microsoft/ORGANIZATION ,/O Nelly/PERSON !/O '/O
Now we notice that microsoft is and organitzation and "," is Other and Nelly is a person's name and so on ..
Now I am asked to return the numbers of tags in the text which is 4 in our case because we have (ORGANIZATION,PERSON,LOCATION,OTHER)
My question here is my logic true ? And since i made a map of String,String ; Is there any way that i can get the size of the values in our case the values are the organization etc.. ?
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
[code].....
Getting Keys From Values In Hashmap
Feb 9, 2014I have one doubt.In HashMap if keys contains 1,2,3,4 and values are a,b,c,d we can get values using get(key) method like 1 will A,2 will return B and so on. Can we get the keys from values like A will get 1 and also if in key if there is a String like 1,2,3,Z and value is A,B,C,7 Z should get me 7. Here I am not using any generics.
View Replies View RelatedHow To Get Method Of HashMap Or Hashtable
Jul 25, 2014How get method of HashMap or Hashtable works internally in Java can any body let me know how does it work..
View Replies View RelatedHashmap Slower After Deserialization?
Feb 15, 2015I have a pretty large Hashmap (~250MB). Creating it takes about 50-55 seconds, so I decided to serialize it and save it to a file. Reading from the file takes about 16-17 seconds now.
The only problem is that lookups seems to be slower this way. I always thought that the hashmap is read from the file into the memory, so the performance should be the same compared to the case when I create the hashmap myself, right? Here is the code I am using to read the hashmap into a file:
File file = new File("omaha.ser");
FileInputStream f = new FileInputStream(file);
ObjectInputStream s = new ObjectInputStream(new BufferedInputStream(f));
omahaMap = (HashMap<Long, Integer>) s.readObject();
s.close();
300 million lookups take about 3.1 seconds when I create the hashmap myself, and about 8.5 seconds when I read the hashmap from file.
Removing A Key From Hasmap Within Hashmap
Dec 1, 2014SO my current code creates a graph with vertices and weighted edges. This data is stored in a hashmap. The key of the hashmap is the vertex and the value is a second hashmap. This second hashmap contains the edges with the vertex it connected to as the key and the weight as the value. My current problem is that when i try to remove vertices they are removed from the key set but they stay in the value(the second hashmap) as the key for that hashmap. IS THERE A WAY TO REMOVE THE VERTEX FROM THE KEYSET OF THE SECOND HASHMAP.
Code is as follows
constructor{
adjacencyMap = new HashMap<V, HashMap<V, Integer>>();
dataMap = new HashSet<V>();
}
removal method{
if(dataMap.contains(vertex)){
[Code]...