Identifying Right Key For Objects / Classes In Application
Jun 12, 2014
I recently had to work on a very simple banking application. Since customers provide their account numbers when they go to the teller to perform a transaction, I chose account number as the key to uniquely identify a customer. To address the fact that a customer can have multiple accounts, I decided to have an entry for every account the customer had, as part of my Teller class, so that he can identify himself with any of his active account numbers. When I was discussing this design with my friend, he felt it was bad and that I had to have a CustomerID field to uniquely identify a customer. I can't seem to understand why we can't do that with account numbers belonging to the customer?
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Mar 1, 2014
I am new to Java and I am doing an assignment to identify Class and Attributes from below example. How to identify 7 classes and its attributes from this scenario:
ABC Maps Maker produces electronic maps for global positioning systems. Every map needs to define the latitude and longitude of the centre of the map, together with the length and breadth of the map. A map also has a name, and a set of geographical features.
A geographical feature is something noticeable in a a map; e.g., a hill, or valley. Among the types of features are the following: trace features, track features and tract features.
All features have a name that is displayed on the map next to the feature. A trace feature has a coordinate point to indicate its location relative to the centre of the map. Broadcasting stations, mountain peaks, and transmission towers, are examples of trace features. Every trace feature has a description associated with it.
Examples of track features include roads, railways and rivers. Each track feature has a list of points that define its course, and a line pattern. The line pattern specifies the colour, and the thickness.
Like a track feature, a tract feature also has set of points, except that when drawn on the map, the last point is linked to the first point to enclose a complete region. Additionally, it has a fill pattern which incorporates essentially a colour.
Recall that there is a class, Point, in the java.awt package – this can be used to hold the co-ordinate of a point
Class:
Attributes:
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Oct 18, 2014
I'm quite new to Java. I have some trouble with understanding how to get two classes to get objects from each other (if that is the correct term).
Lets say I have a login class, in which I have a method checking what the user has entered into the console (I have not displayed the whole code, but this class works as it should and give the user an option to enter username and password and return it true if entered correct).
public static boolean validateUserPass(String userName, String password) {
String[] user = {"admin"};
String[] passwords = {"firkanten"};
boolean check = false;
for (int i = 0; i < user.length; i++) {
if (userName.equals(user[i])) {
if (password.equals(passwords[i])) {
check = true;
Now, in another class I want a display box to appear on the screen and give the user three options: Click yes, no or cancel. I get this to run perfectly alone, this is not the hard part for me. I want the display box only to appear when the correct username and password is given, but I can't seem to figure out how to do this probably.
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Feb 14, 2015
For class, we need to create a word game using classes and objects.
The game is played in rounds. The player is presented with a word that is missing letters. The player has to fill in the missing spaces with their letter guesses. The words presented are chosen with a random number generator which has been provided for us. At the end of the game, the player is shown their score.
In steps, I have to:
-Welcome the player.
-Present the puzzle.
-Allow the player to fill in the blanks.
-Have the program check responses for correct/incorrect input.
-End the game if they have three misses, or continue if they complete the puzzle.
Now, to start, I have a class for the number generator, a class to store the array of 25 words, and a class for the game itself.
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Mar 15, 2015
The question states: Design a class named LinearEquation
for a 2 x 2 system of linear equations:
ax + by = e
cx + dy = f
Where
x =
ed − bf/ad − bc
y =
af − ec/ad − bc
The class contains:
- Private data fields a, b, c, d, e, and f.
- A constructor with the arguments for a, b, c, d, e, and f.
- Six get methods for a, b, c, d, e, and f.
- A method named isSolvable() that returns true if ad−bc is not 0.
- Methods getX() and getY() that return the solution for the equation.
Write a test program that prompts the user to enter a, b, c, d, e, and f and displays the result. If ad − bc is 0, report that "The equation has no solution."
I believe that my program is correct because I am able to compile it and get no errors, however I have no clue how to display the information for x and y or display this equation has no solution if ad-bc=0.
Java Code:
import java.util.Scanner;
public class Exer911 {
public static void main(String[] args){
// Create a scanner system to hold the numbers for each variable
Scanner input = new Scanner(System.in);
// Prompt the user to enter a number for each of the variables
[Code] ....
How to get the information to display ....
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May 8, 2015
I have seen many ways of describing what objects are, one being that objects are a user-defined datatype. However, if objects are datatypes, then what does that make classes? To me, it seems as though classes should be the "types" of data defined by the programmer, and objects should be the specific "values" of that user defined data type. As an example, an integer would be a class, while 1 would be a "value" of that class, i.e. an object. From this point of view, I don't see why a specific number would be a data type... Therefore, why do we say that objects are user defined data types rather than classes?
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Apr 16, 2014
I am working on a class project and I have to write the JUnit test for the GUI class ... what I did wrong ... Here is the code for the GUILauncher:
package edu.oakland.production;
import java.awt.*;
import javax.swing.*;
public class GUILauncher{
public static void main(String[] args){
RetrieveWindow gui = new RetrieveWindow();
[Code] .....
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Nov 22, 2014
I was doing a project in a usual Java Application, but now maybe I have to use some tools that are contained in javafx.scene.media.MediaPlayer so I wonder if can it all work? Will javafx methods and such works?
I have to use javafx.scene.media.MediaPlayer beacuse I have to create a very simple audio player (one jbutton and one jcombobox).
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Jun 18, 2014
Before continuing a task, any more accurate way to identify hashes? Currently, I am using regex + length of hash to give the user possible hashes.
Identifier class:
package votek;
* Purpose: Class is used to run checks on possible hashes that the user has entered.
*/
public class Identifier {
//Hash entered by user is stored here
private String hash;
//String that will contain all possible hashes to share with user
private String results = "Possible Hashes: ";
//Method that runs the other hash methods checks and prints out the results.
[Code] ...
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Oct 27, 2014
Is there a way of detecting the file's type (whether it is a pdf, jpg, png,or anything else) by reading the content of the file. We could read the extension of file to determine it's type, but then extensions can be forged too. So I would like to know if the content inside a file is of a particular type or not. I'm not sure about this, but I have heard somewhere about each having having a specific kind of header which determines its type. So is it possible to read that header and determine it using a program?
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Feb 24, 2015
I am currently taking a computer science class in high school, and its my first time programming (2 weeks since i started). I have currently finished my program however there were a few details that bothered me. I was supposed to create a program which can calculate average of individual marks and then calculate all of the average marks previously entered by user. However I noticed something that bothered me, which was the fact that if i were to enter a number when asked to enter a name, it would assume that number is a name. Also when I asked for the 5 marks the program would run fine until an error occurs if i accidentally type in a letter or word. I have done some research and found system scanners however i still don't understand the concept in a looping situation. Here is what I have so far.
import java.io.*;
public class loopingEx6Final {
public static void main(String args[]) throws IOException{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
double average, totalaverage = 0;
int Mark, Marktotal=0, marktotalsum=0, count=0;
[Code] .....
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Apr 9, 2015
I've written a java application with several classes all in the same .java file. It works just fine. Now, I've broken it up so that each class has its own .java file. Still works fine. My next step is to put those classes into a package, but I'm not about to get the program to run.The .java source files are all in /home/user/src
I've set the CLASSPATH to /home/user/src..All of the source files have "package com.myfirm.program" on the first line.I compiled the application with:
javac -d . File1.java File2.java File3.java (etc...)
the compiler created the directory: /home/user/src/com/myfirm/program and put all of the .class files in there.So how do I get the program to run? if I run from /home/usr/src
java File1
I get: Exception in thread "main" java.lang.NoClassDefFoundError: File1 (wrong name: com/myfirm/program/Program)
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Jul 27, 2014
I am currently working on a project where I need to return data from a database over RMI to a client who requests it. Some of the fields in the Data Object can not be seen by the client so I need to create another object to send over the network instead. The method I use is this...
public static SerializableObject createSerializableObjectFromDataObject(DataObject dataObject){
SerializableObject serializableObject = new SerializableObject();
serializableObject.setField(dataObject.getField());
serializableObject.setAnotherField(dataObject.getAnotherField());
return serializableObject;
}
Is there a better way of doing this? I am creating many subclasses DataObject which all require this static method to be implemented and I can't push it into the superclass because each one needs custom behaviour.
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Apr 18, 2014
How do you call classes within other classes? Or can you only call classes through the main?
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Nov 17, 2014
convert or move standalone java thread application into Tomcat server container for accessing its JNDI services? Also is it possible to schedule this thread application in Tomcat server? is it possible to keep this app in tomcat as web application and schedule in window's scheduler.
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Mar 11, 2014
I am new to work on JNLP program. I have created a SWING program, JNLP file when i deploy the ear file i am getting 404 error. Please find the steps in details.
1.Created a dynamic web project JWStartProject in eclipse
2.Create a HelloWorld.java class under default package.
import javax.swing.*;
public class HelloWorld extends JFrame {
private static final long serialVersionUID = 4968624166243565348L;
private JLabel label = new JLabel("Hello Java Web START!");
public HelloWorld() {
super("Jave Web Start Example");
this.setSize(350, 200);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE );
this.setLayout(null);
[Code] ....
Now I exported this project as JWStartProject.war contains following code.
Created Server in Websphere Admin console
Deployed this war file under the server and started.
I have added MIME types also.
I am unable to launch the application. I am getting 404 errors. May I know where I went wrong?
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Feb 14, 2015
I'm doing an aggregation exercise that's suppose to find the volume and surface area of a cylinder. What I'm trying to do is pass values from one class, to a second class, and that second class passes values to a third class.
This may be a clearer explanation: The first class is the main program which sends values to the second and third class. The second class is used do calculations for a circle (a pre-existing class from another assignment). The third class grabs the values that the second class calculated and calculates those values with the one that was passed from the first class to the third class. The first class then prints the outcome.
Problem is when the program gets to the third class, it just calculates the value from the first class with the default constructor from the second class. It's like the second class never received the values from the first class. I think I'm missing a step, but I don't what it is.
First Class:
package circle;
import java.util.Scanner;
public class CylinderInput
{
static Scanner in = new Scanner(System.in);
public static void main(String[] args)
{
//user defined variable
[Code]...
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Jan 23, 2015
how String objects are different from other objects
part 1:
// creating two objects
Dog mydog1 = new Dog();
Dog mydog2 = new Dog();
// comparing the reference variables
if( mydog1 == mydog2){
System.out.println(" The reference variables refer the same object ");
}
else {
System.out.println(" They refer to different objects ");
}
The above code works as I understand objects , it prints "They refer to different objects " to the screen.
Part - 2
// creating two objects ( I beleive, pls correct me if i am wrong )
String a = "haai";
String b = "haai";
if( a == b){
System.out.println(" Reference variables refer to same object");
When i run the above code it prints that a and b refer same object , I don't understand how they refer to same object when i didn't assign " String b = a; ". My question is did java just create one object and stored the same reference values to a and b .
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Dec 26, 2014
Why do we get such output or which line of code produces the output?
1class Egg2 {
2 protected class Yolk {
3 public Yolk() { print("Egg2.Yolk()"); }
4 public void f() { print("Egg2.Yolk.f()");}
5 }
6 private Yolk y = new Yolk();
[Code] ....
/* Output:
1.)Egg2.Yolk()
2.)New Egg2()
3.)Egg2.Yolk()
4.)BigEgg2.Yolk()
5.)BigEgg2.Yolk.f()
*///:~
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Feb 7, 2014
Regarding the code examples in Head First Java, this is from Chapter 5, regarding the beginning creation of the dot com game. There are two classes in quesiton
the first is the SimpleDotComTester class:
public class SimpleDotComTester {
public static void main(String[] args)
{
SimpleDotCom dot = new SimpleDotCom();
int[] locations = {2, 3, 4};
dot.setLocationCells(locations);
String userGuess = "2";
String result = dot.checkYourself(userGuess);
}
}
and the second one is the code for the checkYourself () method in the SimpleDotCom class
public class SimpleDotCom {
int[] locationCells;
int numOfHits = 0;
public void setLocationCells(int[] locs)
[code]....
Now I noticed that both classes use a variable called result; the program runs fine, but assume from the example that you can use the same variable name two different classes;
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Mar 29, 2014
design a class to conduct a survey of three hospitals. you want to know how many sectors (eg operation, children, gastronomic) each hospitals have, and how many doctors there are in each sector.
what is the process of class design?
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Jan 5, 2014
I have a Date class and Time class. Is it possible to pass Time object inside Date constructor so that toString function gives output as 12/05/2013 06:31:30 ?
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Apr 24, 2014
I have two classes.
First and Second.
In First class I want to use methods from Second class. So:
Java Code:
Second s = new Second();
s.secondMethod(); mh_sh_highlight_all('java');
Second thing I want to do is use JTextArea from First class in Second class.
So since it gives me error, I extended First class with Second:
Java Code: public class Second extends First { mh_sh_highlight_all('java');
It look like it should work, no errors etc. Also both things are working separately. But since I used both at once...
Java Code:
Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
at package.Second.<init>(Second.java:7)
at package.First.<init>(First.java:17) mh_sh_highlight_all('java');
I can move what I need to First class, and it will work fine, but I want to make this in two classes. But I really don't understand extends, I just use them if there is need for them. So I don't know how to handle this problem.
I also tried to extends Second just like First:
Java Code: public class Second extends JPanel implements ActionListener { mh_sh_highlight_all('java');
Instead of extending First, but it can not be done, since ActionListener is in First...
Well. Also addActionListener can maybe solve my problem?
I'm using:
Java Code: xx.addActionListener(this); mh_sh_highlight_all('java');
Maybe I can use something instead of this? But what?
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Jan 19, 2015
Wondering, what is exactly reason for existence of inner classes? Are there problems that without them you can not resolve?
Anything beside emulate multiple inheritance - when your class need to extends the real classes, and not implement multiple interfaces ?
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Mar 28, 2015
I have a folder of classes that I am packaging together. Some classes are being packaged and compiling just fine. My other classes in the same package, however, are saying that they cannot find these classes.
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Apr 12, 2015
What i'm trying to do is to pass a bufferedreader string from main method to a class that will set on how fast or slow a message will be displayed but it has to be displayed on a JTextArea that's in a constructor class.
import java.awt.*;
import javax.swing.*;
public class demo {
JFrame frame = new JFrame ("Idle Game Test!");
JPanel backGroundPanel = new JPanel ();
JPanel statusPanel = new JPanel ();
JPanel buttonPanel = new JPanel ();
JPanel bigPanel = new JPanel ();
JTextArea message = new JTextArea ();
[code].....
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