I'm learning Java using BlueJ, I have made a class that has a HashMap of (String, String) that contains an the make of a car and the model.
I want a method to return a collection of all the keys that satisfy a condition, like if someone wants to find what make a certain model is. I know it requires a loop, just not too sure how to write the loop to satisfy the condition.
I 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 RelatedHere is my HashMap and a method for listing all the keys in it
HashMap<String, String> exampleOne = new HashMap<String, String>();
public void allKeys() {
int i;
i =0;
for (String name: exampleOne.keySet())
[Code]....
Now I want to return all values that associated with one key. How do I do this? Or is it possible to other way round? I mean return All keys associated with a value?
I have a simple question but I dont understand why I am getting false for this boolean statement.
System.out.println("hash compare " + (trialSearch.returnHash() == fish.returnHash()));
System.out.println("fish.returnHash()" + (fish.returnHash()));
System.out.println("trialSearch.returnHash()" + (trialSearch.returnHash()));
the output is as follow:
hash compare false
fish.returnHash(){T=[1, 2, 3, 5], G=[], A=[0], C=[4]}
trialSearch.returnHash(){T=[1, 2, 3, 5], G=[], A=[0], C=[4]}
why is it printing false for the boolean statment when the two hashmaps contain the same values and keys?
I am currently trying to implement a hashmap from a class i currently have that is called 'Paper'
My paper class consists of:
String Title;
String[] author;
What I am wondering, is if there is anyway I can call these seperate attributes to be both the key and the value of the hashmap. Currently I cannot see a way to call individual values, only the class itself.
my query is like: "i want to create hashmaps where the inner hashmap contains the key as firstname and value as a Class Student which contains parameters firstname, lastname,etc. I need this hashmap to be accessed by other objects of different classes".
public class Student {
private String FirstName;
private String LastName;
private String EmailAddress;
private String PhoneNumber;
private String Username;
private String Password;
private String EducationalInstitution;
[code]....
As we give the values by Scanner, it should be Stored in Hashmap and how those values can be accessed by other object classes?How does the Logic works? What my next step?
So I am learning HashMaps/Arraylists and I can't really understand the diamond operator or what it's for. Take the following code for example: Why could we not just do this without the diamond?
Java Code:
import java.util.HashMap;
class Untitled {
public static void main(String[] args) {
HashMap<String, String> map = new HashMap<String, String>();
map.put("California","Sacramento");
map.put("Oregon","Salem");
map.put("Washington","Olympia");
System.out.println(map);
}
} mh_sh_highlight_all('java');
I am having an issue with my swing gui. I dynamically create tabs with information (textfields, checkboxes, combo boxes) and when I select the checkbox it disables or enables a textfield. Now when I select the checkbox it seems to resize everything, specifically my textfields from say 9 columns to probably one. I"m a little unsure why it is doing this but I have a feeling it may be an inheritence issue.
My code is below for my generation of the tabs and of the rest of the information on the gui. The gui is an inner rid layout with a top and bottom pane that are both gridbaglayouts and an outter pane as well. I am thinking I am missing something in the grid layout setup that is causing this.
private void initComponents() {
jTabbedPane1 = new javax.swing.JTabbedPane();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
getContentPane().setLayout(new java.awt.GridLayout(1, 0));
pack();
[code]....
How can I populate the jTable in my form by selecting value from combo box. And remember I have database as well.
View Replies View RelatedI have a selection listener attached to a TreeView as shown below
treeView.getSelectionModel().selectedItemProperty().addListener(new ChangeListener<TreeItem<Pair<VideoSourceType, String>>>() {
@Override
public void changed(ObservableValue<? extends TreeItem<Pair<VideoSourceType, String>>> observable, final TreeItem<Pair<VideoSourceType, String>> oldValue, final TreeItem<Pair<VideoSourceType, String>> newValue) {
// do something
treeView.getSelectionModel().clearSelection();
}
};
What I want to do is to "do something" and then clear the selection so that it can be selected again. However, I cannot re-select the same item from the TreeView until I first select a different item.
I want to render a specific region of an image in LWJGL,
View Replies View RelatedWhat it's supposed to do: This code is supposed to see if the clicked card is selected. If it's not, select it and show the player where it can move / attack. If it is selected, then find out what card the player clicked on. If he clicked on the card that was already selected, deselect it. If he clicks on a friendly card (same playerID), then select that card. If he clicks on an enemy card (different playerID), attack that card. If he clicks on a tile, move it to that tile.
The problem: However, line 24-58 give me a bit of a problem. Right now, it works fine BECAUSE lines 46-58 are commented (which also means the unit can't move). If I uncomment those lines, the unit becomes able to move, however, lines 34-46 cease working...
Java Code:
@Override
public void mouseClicked(MouseEvent e) {
mainloop: for (int i = 0; i < Main.cards.size(); i++) {
Card c = (Card) Main.cards.get(i);
if (Card.cardSelected == null) {// Contains / Is not selected
if (c.contains(e.getX(), e.getY())) {
Tile.reset();
Card.reset();
Card.cardSelected = c;
[Code] ....
I 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].....
I am writing a code that tries to figure out the users password by going through every possible key (brute force). Although I think its going to work, it looks EXTREMELY inefficient to me, since its just a huge switch statement for each character -- 94 total, including the shift values. Is there a built in method in the JAVA API that goes through every key or something?
Here is my code for that segment:
public char[] HackingPassword(){
char[] passChars = this.password.toCharArray();//convert the password to char[]
char[] hacking = new char[passChars.length];//make the hacking variable same size as users password
int nextCharValue = 0;//this is used to cycle through the keyboard
//check each letter of hacking to match with password
for(int i = 0; i < passChars.length; i++){
[Code] .....
I am new with java, eclipse, jpa(eclipselink), postgresql, and trying to make a web application. I have two tables:
bids: id, quantity, price
trades: bidid, askid, quantity, price
bidid and askid columns are foreign keys from bids table (id), and they are the primary key for the trades table.
I created the Entities from the Tables (Bid and Trade class) with eclipse and it generated a TradePK class for the primary key.
Trade.java:
@Entity
@Table(name="trades")
public class Trade implements Serializable {
@EmbeddedId
private TradePK id;
[Code] ....
I understand that this is necessary because the primary key is from two column, but as soon I want to persist a Trade back to the database Eclipselink call the column names twice:
INSERT INTO trades (price, quantity, datetime, BIDID, ASKID, bidid, askid) VALUES (?, ?, ?, ?, ?, ?, ?)
So postgres give me back an exception: ERROR: column "bidid" specified more than once
And I don't know why. According to the JPA docs I didn't found any mistake:
Introduction to EclipseLink JPA (ELUG) - Eclipsepedia
Or I just can't see it... or is there a better doc which explains it better?
I want to write a method to print the all the names of a phone book. phoneBook is a HashMap<String, String> , that has names as keys and phone numbers as values.
Reading the documentation for both HashMap and Set, I have more or less an idea of how it could be done but I cant put it on code..
public String getName()
{
String[] keys = phoneBook.keySet().toArray();
return keys[0];
}
This is wrong. It doesnt compile saying incompatible types. I was thinking first to manage to succeed to get a key from my phone book and then I change it to print all the keys.
I am trying to work with a SQL database and some JSF pages that were created with/for CRUD. The data comes up just fine but all my foreign keys show the primary key for the key not the data. So instead of having the actual Zone I get the number (my primary key) that matches the Zone.
example:
4717A Cool ReceptionTitle: Gatherer of Cool Companycom.vancowboy.lotor_db.LotroZones[ id=11 ]
The last item should read "All" not "com.vancowboy.lotor_db.LotroZones[ id=11 ]"
This was straight from a tutorial so I can learn this but the FK has got me baffled...
I have the following hashMap declared:
private HashMap<String, Car> cars = new HashMap<String, Car>();
How can i get an array of String filled with hashMap keys?
I Want to identify up, down, left and right keys with the keylistener() WHATE NAME DO I IDENTIFY IT WITH
View Replies View RelatedI am developing a java code using netbeans for encryption decryption by RSA algorithm. Swings and file handling play a major role in these code. My encryption code is working nicely but the code for decryption is not since keys file is not being read. That is why variable mod and pri are getting null values and the following error stack is coming. I know where the problem is somewhere in void readkeys() function but cannot solve it.
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.math.BigInteger.modPow(BigInteger.java:1579)
at rsakeydecryption1.RsaKeyDecryption.decryption(RsaKeyDecryption1.java:167)
at rsakeydecryption1.RsaKeyDecryption.read_output(RsaKeyDecryption1.java:294)
at rsakeydecryption1.RsaKeyDecryption.actionPerformed(RsaKeyDecryption1.java:330)
[Code] .....
My code for decryption is
package rsakeydecryption1;
import java.math.BigInteger;
import java.util.Random;
import java.io.*;
import javax.swing.*;
[Code] ....
Suppose that a certain BST has keys that are integers between 1 and 10, and we search for 5. Which sequence below cannot be the sequence of keys examined?
(a) 10,9,8,7,6,5
(b) 4,10, 8, 6, 5
(c)1,10,2,9,3,8,4,7,6,5
(d) 2,7,3,8,4,5
(e)1,2,10,4,8,5
I've noticed many differences, such as there is only one with an odd number of keys, and one has all integers from 1-10 inside of it, but I can't find any real reason that you wouldn't be able to search it?
I've started creating a simple game in Java, so now I'm stuck. I wanted to make moving character by fast alternating arrow keys, but I don't know how. I can make a boolean variable, which disables moving by pressing the same key again, but the player can just hold the key and character is still moving. I thought about changing position of character when the key is pressed, instead of increasing speed, but then the movement wouldn't be smooth. I think this may sound incomprehensible, so I will add a link to game like an example of what I mean.
Play Mini Sports Challenge game online - Y8.COM
I need to get a clone of a fairly deep object tree. All objects are entities and I need to set the primary keys to null. The root object:
public class Grundentscheidung implements Cloneable {
@OneToMany(cascade = CascadeType.ALL)
@JoinColumns({
@JoinColumn(name = "gesamtentscheidung_dstNr"),
@JoinColumn(name = "gesamtentscheidung_id")
[Code] .....
When I call
Grundentscheidung grundentscheidungClone = grundentscheidung.clone();
grundentscheidungClone contains the whole object tree with all dependencies, but the Tatbestand objects have their primary keys. When I use the debugger I see that Tatbestand.clone() is never called.
Is my code faulty? I would like to avoid to write a large method which sets all primary keys on the object tree to null.
I've visited this great site been following this java tutorial on making the snake game, and as I followed along at added the second player. Right up to the point I got into the resetting if I hit borders or myself or the other player, the snakes stopped moving when i tried hitting keys...problem started up to the point where I added snake2 in the GenerateDefaultSnake method
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.LinkedList;
import java.util.Random;
[code]....
My objective here is to process a HashMap's key's in order. I found SortedSet as a way to do it.
The HashMap is like this:
nobelPrizeWinners = new HashMap<String, PrizeWinner[]>();
// 2009:
nobelPrizeWinners.put(new String ("2009 Physics"), new PrizeWinner[] {new PrizeWinner("Charles K.", "Kao"), new PrizeWinner("Willard S.", "Boyle"), new PrizeWinner("George S.", "Smith")});
[Code] ....
This is the method I am trying to write
public void displayAllYearsAndWinners_2()
{
// Creation of the SortedSet
SortedSet sortedSet = new TreeSet();
[Code] ....
However, the compiler gives me a warning of NobelPrizeWinners.java uses unchecked or unsafe operations. Recompile with -Xlint:unchecked for details.
As I said, my objective here is to process them in order. If this compiler warning cannot be resolved, I am open to other methods of accomplishing my objective.
I'm working on a Java 2D game which requires a max of six keys be held down at the same time.
The game is for two players on the same keyboard, playing simultaneously.
However, all three computers I ran the program on only allow a max of three keys held at a time. They all have trouble with reacting to more than three keys being held.
It seems that pressing a new key after three are already held, either cancels some other key-holding or is ignored.
I've been told that this is a hardware issue. Most keyboards can't handle more than three keys held at a time. But a lot of games do require this, and they do not require special gaming-keyboards to run on my computer without problems.
So there has to be a solution that will make the game playable on any standard keyboard.
(I use Key Bindings).
The game's controls:
Player 1
- Rotate sprite and set angle of movement: LEFT arrow
- Rotate sprite and set angle of movement: RIGHT arrow
- Move forward: UP arrow
- Shoot missile: ENTER key
Player 2
- Rotate sprite and set angle of movement: 'A' key
- Rotate sprite and set angle of movement: 'D' key
- Move forward: 'W' key
- Shoot missile: 'T' key
Relevant code:
The Key Bindings part:
Java Code:
// An action for every key-press.
// Each action sets a flag indicating the key is pressed.
leftAction = new AbstractAction(){
public void actionPerformed(ActionEvent e){
keysPressed1[0] = true;
[Code] .....
This is mostly how reacting to key-presses and key-releases works in my program. When a key is pressed or released, a flag is set. The Board class reades the flags every game-loop cycle and reacts accordingly.
As I said, the program doesn't react correctly to more than 3 keys held at a time, probably because of the keyboard. Is there a way to code a solution?