New ArrayList Java Collection Types
Jun 26, 2014
I am looking at a snippet of code in my "learning Java 4th edition" by Orielly and there is a small snipped of code which says:
Java Code: Date date = new Date();
List list = new ArrayList();
list.add( date );
..
Date firstElement = (Date)list.get(0); // Is the cast correct? Maybe. mh_sh_highlight_all('java'); so I am typing the same thing in my compiler in a small Driver class and for some reason I have an error and Im dumbfounded...
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Aug 25, 2014
I would like to create an ArrayList from data types stored in a text file.The ArrayList would be multidimensional with two data types; int, String.
Example text file could be:
4 cahiers grand format
3 stylots bic bleu
5 gommes
I find it very difficult for multiple data types i don't see how its possible.
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Feb 28, 2014
I'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] ....
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Nov 18, 2014
So I have a persons class:
public class Person
{
private String name;
private int age;
public Person (String name, int age) {
this.name = name;
this.age = age;
[Code] .....
And I need to write a simple main method that creates lots of instances of the Person class and adds them to a generic instantiation of a Collection (ArrayList). And I need to make it so I as a programmer can define how many instances to create.
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Nov 16, 2014
I have declared an array list that will store data type of 1 Character and 2 integer. The data that will be store in this list is
1. A = {0 3}
2. B = {0 5}
3. C = {0 3}
4. D = {0 3}
5. E = {0 5}
6. F = {0 6}
Now here the alphabets are routers and integers are there con1 and con2 respectively. I have a set of router={ A,B,C,D,E,F}.
Step 1:I have to subtract con1 from con2 i.e. (3-0) of all the routers and
Step 2: then put the router having largest value in new set 1 and
Step 3: then this router will be subtract from the router set.
Step 4:then again I have to repeat the step 1 until the value of routers become <= 1.
Now what I did is I defined 3 arrays first is String array that stores names of routers, 2nd array that stores the first value and 3rd array that stores the second value. I can find the largest value but how to store the name of router against the largest value in the set.
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Sep 1, 2014
I am trying to remove the duplicate elements from ArrayList using .contains() if elements are primitive datatype it works but user-defined datatype does not work.
public class UserBean {
String name;
String address;
public String getName() {
return name;
[code]....
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Apr 20, 2015
I have Date as listed below:
17/03/2015 09:38:39 AM
17/03/2015 10:52:26 AM
10/03/2015 08:30:56 AM
02/03/2015 09:18:10 AM
02/03/2015 09:37:23 AM
02/03/2015 11:25:01 AM
02/03/2015 11:29:00 AM
02/03/2015 11:42:38 AM
02/03/2015 12:04:39 PM
02/03/2015 12:09:05 PM
02/03/2015 01:17:09 PM
02/03/2015 01:29:08 PM
I want them to sort them as per below result: (Same date one should be sort by timestamp)
17/03/2015 10:52:26 AM
17/03/2015 09:38:39 AM
10/03/2015 08:30:56 AM
02/03/2015 01:29:08 PM
02/03/2015 01:17:09 PM
02/03/2015 12:09:05 PM
02/03/2015 12:04:39 PM
02/03/2015 11:42:38 AM
02/03/2015 11:29:00 AM
02/03/2015 11:25:01 AM
02/03/2015 09:37:23 AM
02/03/2015 09:18:10 AM
I tried using Collection.sort using compareTo but result is not expected...
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Apr 20, 2015
I have Date as listed below:
17/03/2015 09:38:39 AM
17/03/2015 10:52:26 AM
10/03/2015 08:30:56 AM
02/03/2015 09:18:10 AM
02/03/2015 09:37:23 AM
02/03/2015 11:25:01 AM
02/03/2015 11:29:00 AM
02/03/2015 11:42:38 AM
02/03/2015 12:04:39 PM
02/03/2015 12:09:05 PM
02/03/2015 01:17:09 PM
02/03/2015 01:29:08 PM
I want them to sort them as per below result: (Same date one should be sort by timestamp)
17/03/2015 10:52:26 AM
17/03/2015 09:38:39 AM
10/03/2015 08:30:56 AM
02/03/2015 01:29:08 PM
02/03/2015 01:17:09 PM
02/03/2015 12:09:05 PM
02/03/2015 12:04:39 PM
02/03/2015 11:42:38 AM
02/03/2015 11:29:00 AM
02/03/2015 11:25:01 AM
02/03/2015 09:37:23 AM
02/03/2015 09:18:10 AM
I tried using Collection.sort using compareTo but result is not expected.
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Aug 6, 2014
I am currently working on a Java project, below are my attempts at coding so far:
public class MyZoo
{
// zoo identifier
private String zooId;
// a number used in generating a unique identifier for the next animal to be added to the zoo
private int nextAnimalIdNumber;
// zstorage for the Animal objects
private TreeMap<String, Animal> animals;
[Code] ....
I currently cannot get the printAllAnimals() method to work as it should.
When executing the method printAllAnimals(), it does not do anything, when it is supposed to use the Collection object c, so that animals stored in the zoo can easily be checked.
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Feb 11, 2014
How to implement HashMap put and get methods without using Java Collection framework?
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Jan 10, 2010
I've got a CDI bean which is a facade for a JPA entity. Such entity has got a many to one relationship with itself and I've got the following method:
public Set<Account> getChildren() {
return this.children;
}
which is called in a JSF/Facelets page:
<h:commandLink action="#{accountController.destroy}" value="#{bundle.ListAccountDestroyLink}" rendered="#{item.children.size() == 0}"/>I then decided to return an unmodifiable set and changed getChildren() accordingly:
public Set<Account> getChildren() {
return Collections.unmodifiableSet(children);
}
The page now reports this error:
java.lang.IllegalAccessException: Class javax.el.BeanELResolver can not access a member of class java.util.Collections$UnmodifiableCollection with modifiers "public"
at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:65)
at java.lang.reflect.Method.invoke(Method.java:588)
[Code] ....
javax.el.BeanELResolver is incorrectly failing because it's trying to invoke the size() method using reflection without correctly taking into account the method visibility (which is indeed invokable programmatically). I'm running NetBeans 6.8, Glassfish 3.0 and jdk1.6.0_17.
Is this a bug in BeanELResolver?
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Apr 25, 2014
I need to retrieve all Line Strings from a Geometrical Collection(of line strings) lying between two coordinates (Coordinates are taken from existing Line Strings in the Geometrical Collection).
I am using JTS library. I tried intersection() function but it worked only for linear geometries not for curved. How to get the output in the most efficient way.
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Apr 1, 2014
I am trying to understand the concept of Generics in java. In the introduction to Generic Types, this example is given:
Java Code: public class Box {
private Object object;
public void set(Object object) { this.object = object; }
public Object get() { return object; }
} mh_sh_highlight_all('java'); "Since
Since its methods accept or return an Object, you are free to pass in whatever you want, provided that it is not one of the primitive types." - I understand this.But then it has been changed to a generic class:
Java Code: /**
* Generic version of the Box class.
* @param <T> the type of the value being boxed
*/
public class Box<T> {
// T stands for "Type"
private T t;
public void set(T t) { this.t = t; }
public T get() { return t; }
} mh_sh_highlight_all('java'); "
As you can see, all occurrences of Object are replaced by T. A type variable can be any non-primitive type you specify: any class type, any interface type, any array type, or even another type variable."We can use any type in place of an Object, because Object is a superclass of all classes. But T (or any other class) is not a superclass of all classes. So how do we justify any class being used in place of a random T or any other class?
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Jun 30, 2014
how many types of inputting method in java?can you explain with examples?
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Jan 20, 2015
I thought numeric literal were by default int or doubles, depending on if have a . and numbers after the But I wrote a quick test program as listed below. I understand the float float floatA = 5.5; failed to compile since 5.5 is a literal of type double and you are trying to assign this to a floag
What I am having problems with is byte byteA = 5; 5 is a literal of type int and this is being assigned to a byte and compiler should complain.The compiler does not allow two byte values to be added and assigned to a byte since the result of the addition is an int
class literalTesting{
public static void main(String[] arg){
byte byteA = 5; // allowed WHY I thought literal is an int and assigning int to byte
byte byteB = 10; // allowed
[code]...
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Sep 7, 2014
I need to write a simple program that displays up to 5 pairings of data types (int, string) (string, long) ect. I need to have at least two classes, a Pair class (generic) and an PairTest class.
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Aug 10, 2014
So I have been busy at some projects lately. One of them having this projectill put up the full code and the part i have problems with:
package relax;
//importeverything
import java.awt.AWTException;
import java.awt.Robot;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
[code]....
There is some kind of issue here.in the gui it will ask you to give points in time (ms) it wants to click for you, although when for example i put in 3 at "How Much Clicks" it asks 4 times and then exits with an error.Here is the error:
Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 3
at relax.Relax.StartSetup(Relax.java:175)
at relax.Relax$2.actionPerformed(Relax.java:78)
at javax.swing.AbstractButton.fireActionPerformed(Unk nown Source)
at javax.swing.AbstractButton$Handler.actionPerformed (Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed (Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseRe leased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
[code]....
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Feb 14, 2015
I have small project to be implemented in Java, which, expected the management of a parking.
The project has a class abstract Vehicle, whence derive three classes: Car, Motorcycle, Heavy Vehicles; the cost estimated time for the 3 types of vehicles are: 2€ for Cars, 1€ for Motorcycle and 5€ for H.V.
In addition, in class Ticket will be stored the arrival time of the customer and the characteristics of his vehicle.
Finally, in the class Parking(which provides 80 places available), here it should be added the various types of vehicles.
Now, I though of using an Collection, as Set.. So that they can not, two Vheicle with same license plate.
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Apr 12, 2015
2 problems with this code:
How do I code this so that after the user has added to the arraylist 'theFruit' if they then press 'V' to view all fruit it includes the default fruit as well as the fruit they've added?
Also in the method 'AddFruit' it only allows me to add 2 fruit before printing. Why is this?
import java.util.ArrayList;
import java.util.Scanner;
public class StkOv {
public static void main(String[] args) {
TheMenu();
[Code] ....
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Jul 22, 2014
I have a method
void method(){
String s =null;
String s1 = new String();
}
In this all the two strings are eligible for garbage collection?
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Feb 27, 2014
I am using mysql database and I have downloaded the library also I have managed to get the database connection and query working. I need to know if I need to create separate classes to add/remove/edit items and view items? Do I need to put my database connection script in every class that I create or should I create methods for both the connection and the queries that will be called in the additional classes or methods that I have?
Below is what I have written so far and it is working, I will change the database and query soon to reflect the task I need to do because I have followed a tutorial.
Java Code:
/**
* cdCollection.java
*/
package org.com.mm00422_prototype;
//Import for the SQL package
import java.sql.*;
//Registering the JDBC driver
//Class.forName("com.mysql.jdbc.Driver");
[code]....
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Feb 23, 2015
I have a method that accepts JSONArray as parameter and returns the values of it as ArrayList Object. My question which of these ways is appropriate in populating the ArrayList object this method populates the arraylist upon creation of object (I don't know what the right term to use, but as netbeans IDE suggest, JSONArray object should be final since it was used in inner class.).
private List<String> getStringList(final JSONArray jsonArr) {
return new ArrayList<String>() {
{
try {
for (int i = 0; i < jsonArr.length(); i++) {
add(jsonArr.getString(i));
}
} catch (JSONException ex) {
ex.printStackTrace();
}
}
};
}
this second method is the usual way of populating collection
private List<String> getStringList(JSONArray jsonArr) {
List<String> strList = new ArrayList<String>();
try {
for (int i = 0; i < jsonArr.length(); i++) {
strList.add(jsonArr.getString(i));
}
} catch (JSONException ex) {
ex.printStackTrace();
}
}
What are the advantages and disadvantages between the two? like which is faster? or which consumed larger memory?
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Aug 27, 2014
i am interested to add integer objects and String objects into any collection object ..... while iterating the collection object i am not interested to do any type cast in java
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Apr 13, 2015
With my code the menu runs. But when the user has typed in the name of a fruit (to reserve it) I'd like it to say 'Reserved' when the user then presses 'V' (to go and view all fruit)I have read Oracle Java Collections Arraylist and from my understanding I either have to code using the get method or equals method but I'm not too sure how to (I did try though)
import java.util.ArrayList;
import java.util.Scanner;
public class FruitApril {
public static void main(String[] args) {
[code]...
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Jan 24, 2014
I just started playing around with Java for awhile, but got caught up in a problem when using ArrayList.
CinemaAppMain
public class CinemaAppMain {
public static void main(String[] args) {
new CinemaApp().start();
[Code]....
I am trying to get the movie name and theatre title from their ArrayList, and I know I need to go through the movie list & theatre list to find their name & title, and compare it with the user input and print out the result.
I use for(int i=0;i<movies.size();i++) to go through the the movie list, and I tried using for(int i=0;i<theatres.size();i++) to go through the theatre list. But when I printing multiple time with different user input value, it will show me strange result (screening have same movie name & theatre name, the else if statement is printed below the user input, user input is printed more than once after the first time).
Edit: I know its wrong for me to use nested for loop,if not, another solution is needed to get the item inside both of the list. (getting the "title" from movie list & "name" from theatre list)
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Nov 26, 2013
In my applications garbage collection logs, I see below line.
2013-11-26T10:35:45.050-0500: 5195.298: [GC 5195.298: [DefNew: 17430K->456K(19136K), 0.0102408 secs] 796185K->779211K(2668480K), 0.0103687 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
2013-11-26T10:36:10.593-0500: 5220.840: [GC 5220.840: [DefNew: 17480K->398K(19136K), 0.0100548 secs] 796235K->779153K(2668480K), 0.0101835 secs]
The last line seems half cut. Does that indicate that there is memory leak in my application? I have not seen the app throwing the out of memory error.
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