Overriding Inherited Methods
Feb 5, 2015So the first thing I would like to ask about is overriding inherited methods. I am asked to override methods in one of my assignments and I am not really sure how to go about doing it.
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Do Inherited Methods Use Their Instance Variables?
Jan 8, 2014Do inherited methods use their instance variables or do they use the ones in the method that inherits them?
For example, Class B extends Class A. Class A and B both have the instance variable "potato". A client program tries to use method "cut" using an object of Class B, but class B has no cut method. So, class B uses the "cut" method inherited from class A. What I want to know is will that cut class A's potato or class B's?
Warning For Not Overriding Methods
Mar 26, 2014import javax.swing.*;
import java.awt.*;
import javax.swing.event.*;
import java.awt.event.*;
/* display selected number
if selected, bg is green
if not selected bg is pink
*/
[code]....
my compiler is telling me that the getList... method is not being overridden.but when I change the JList<String> to JList and Object to String in the parameters, i get a warning from the compiler that it's an "unchecked call".
Value Inherited Between Different Arraylist Of Same Class
May 14, 2014I have extracted relevant parts of code and outputs, this is the only relevant code for this problem. There is a basic class called SalonData, which contains the fields refereed to. Original data rs. is obtained from an SQL extract, that is populating correctly.
public ArrayList<SalonData> salons=new ArrayList<SalonData>();
ArrayList<SalonData> loc2=new ArrayList<SalonData>();
SalonData salon=new SalonData();
salon.CardRecordID = rs.getString("CardRecordID");
salon.SalonName = rs.getString("Name");
[Code] ....
Printed results after this code is run;
Salons
2022XYZ PTY33 Smith Street319603 9773 2000
loc2
2022XYZ PTY33 Smith Street319603 9773 2000
The code was inteded to populate the phone number in arraylist "loc2", but based on the code, the phone number in arraylist "salons" for Location 2 should still be blank. Question is how did the phone number for this customer in arraylist salons, for Location 2, get populated?
JSF :: Composite Component With Inherited Attributes
Apr 16, 2014I have to create a new custom tag "imageLabeable" as a div contains a GraphicImage and an OutputLabel (primefaces).
Since I want to make it reusable as much as possible, I tried to write, in cc:interface section, all GraphicImage attributes (id, value, binding etc) and some new (GraphicImage is the main component among the two). But after that I have must associate GraphicImage attributes with the attributes created in cc:interface:
<cc:interface componentType="imageLabeable">
<cc:attribute name="value" />
<cc:attribute name="alt" />
<cc:attribute name="width" />
<cc:attribute name="height" />
[Code] .....
As you can see, if I have a lot of attributes I have to write a lot of association. Furthermore, if I see html rendered code with Firebug or similar, I see all of these associations.
Can I inherit these attributes automatically? Or associate it in easier way?
Swing/AWT/SWT :: Error At Class Name - Type JTextField Must Implement Inherited Abstract Method
Oct 27, 2014This code is directly from Swing: I'm using Eclipse and keep getting an error on line 10 saying :
"The type JTextField must implement the inherited abstract method ActionListener.actionPerformed(ActionEvent)."
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
[Code] ......
Overriding Static Method
Aug 30, 2011class One
{
public static void doStuff()
{
System.out.println("One");
}
}
class Two extends One
[code]....
My understanding of static says that static methods cannot be overrriden but the compilation of the above code results in Overriding rule violation error.
Overriding CompareTo From Comparable Interface
Oct 31, 2014Here is my code:
/*
* Implement the Comparable interface on objects of type Order.
* Compare orderId, then productId. The lesser orderId should come first. If the orderIds match, then the lesser productId should come first.
*/
@Override
public int compareTo(Order ord) {
// TODO Auto-generated method stub
if(orderId > ord.orderId){
return 1;
[Code] ....
Here is the output:
Actual: 0
Expected: -1
Actual: -1
Expected: -1
Actual: 1
Expected: 1
Actual: 1
Expected: 1
Actual: 0
Expected: 0
Actual: 0
Expected: 0
In short, the "Actual" is what my code produces and the "Expected" is what it is supposed to produce. As you can see, only the first one is mismatching... I'll admit, the comment section above the method is confusing and I wasn't exactly sure what it wants me to do, but I thought I figured it out. I just don't see how 5/6 of these tests can work and the 6th one not.
Return Statement In Method Overriding
Jan 1, 2015class Base
{
public Base rtc() {
System.out.println("am in parent");
return new Base();
}
}
class Ret extends Base
[Code] ....
Output :
I am in child class but b1.rtc requires b2 to hold the return value y not Ret's object.
Clarity On Overriding Equals Method
Oct 2, 2014For a few days I've been reading about the importance of overriding the equals method. How overriding it actually determines or checks the values stored in the variable. I realize that you can check the values stored in the primitive datatypes with "==", and when you don't override the equals method it acts the same way, right? When used with a reference datatype, "==" or the default equals() method only compares, or sees, if the variable is pointing to the same instance of a class. For some reason, in the examples, what is taking place to actually check the values stored inside the variables.
Here is part of an example (I've added comments for things that are confusing me):
@Override
public boolean equals(Object obj) {
//So we use Object here instead of the class type
// we're overriding this equals method for?
Is this so that we can use it to check different types? (overloading?)
if (obj == this) {
return true;
//Isn't this checking to see if the calling object is the same as the object we're passing to it?
Why doesn't this return false?
}
if (obj == null || obj.getClass() != this.getClass()) {
return false;
}
//How exactly do we check the values stored in each object though?
}
Overriding ToString - Indicate Whether Coin Is Face Up Or Down
Jan 2, 2015what im trying to do is modify the Coin class to override the toString() method so that it indicates whether the coin is face up or face down. For example, "The coin is face up." This is what i have so far:
public class Coin {
public static void main(String[] args) {
Coin coin = new Coin();
for (int i = 0; i < 1; i++) {
coin.flip();
System.out.println(coin);
[Code] .....
Overriding Equals Method From Object Class
May 5, 2014I am attempting to override the equals method from the Object class which checks if two variables point towards the same object. I want the method to check if if the argument being passed in(an object) has the same data(instance variables) as the object that's calling this method. A NullPointerException is being thrown; Here is the code.
package javaapplication5;
import java.text.NumberFormat;
import java.util.Scanner;
import java.lang.Object;
public class Product {
private String product;
private String description;
private double price;
[Code] ....
And here is the stack trace
Exception in thread "main" java.lang.NullPointerException
at javaapplication5.Product.equals(Product.java:42)
at javaapplication5.Product.main(Product.java:24)
Java Result: 1
Overriding - Use Public Access Modifiers With String
Apr 2, 2015Why do we use public access modifiers with String toString() method in java while overriding???
View Replies View RelatedOverriding Java ToString Method For Web Browser
Mar 14, 2014How do i print override the toString for WebBrowser as i would like to print out the object bc. Tested the program and it is fine if i put it in the main method rather than the WebBrowser constructor.
import java.util.*;
class ListNode <E> { /* data attributes */
private E element;
private ListNode <E> next;
/* constructors */
public ListNode(E item)
{ this(item, null);
[code]...
Overriding In Java - Foo Method Of Class X Is Not Throwing Compile Error
Jul 29, 2013class SubB{
public void foo(){
System.out.println(" x");
}
}
public class X extends SubB {
public void foo() throws RuntimeException{
super.foo();
if(true) throw new RuntimeException();
System.out.println(" B");
}
public static void main(String [] args){
new X().foo();
}
}
Why the foo method of class X is not throwing a compile error because according to the override rule, if the superclass method has not declared exception, the subclass method can't declare a new exception...
Overriding Equals Method - Cannot Invoke Equals On Primitive Type (double)
Jan 7, 2014I am trying to override the equals method for my class TeamMember I have two fields:
private Details details;
private double salary;
Code for override I get an error on salary saying cannot invoke equals (double) on the primitive type (double)
Is their something I am missing/coding wrong?
Java Code:
public boolean equals(Object obj) {
//test exceptional cases
//avoid potential NullPointerException/ClassCastException
if ((obj == null) || (this.getClass() != obj.getClass()))
return false;
TeamMember other = (TeamMember) obj; //cast to a TeamMember object
// compare fields details and salary
return this.details.equals(other.details)
&& this.salary.equals(other.salary);
} mh_sh_highlight_all('java');
Altering Parent Method Behavior By Overriding Method It Calls
Apr 21, 2014I have two classes (Daughter and Son) that contain some very similar method definitions:
public class Family {
public static void main(String[] args) {
Daughter d = new Daughter();
Son s = new Son();
d.speak();
s.speak();
[Code] .....
Each of those classes has a "speak" method with two out of three lines being identical. I could move those into a parent class, but I need each of the child classes to continue to exhibit its unique behavior. I'm trying the approach below, which replaces the unique code with a call to a "placeholder" method that must be implemented by each child class:
public class Family {
public static void main(String[] args) {
Daughter d = new Daughter();
Son s = new Son();
[Code] .....
This works and moves the shared code from two places (the Daughter and Son classes) into one place (the new Mother class, which is now a parent class of Daughter and Son). Something about this feels a bit odd to me, though. It's one thing for a child class to override a parent class's methods to extend or alter their behavior. But, here, I've implemented an abstract method in the parent class to alter what happens when the parent class's method (speak(), in this case) is called, without overriding that parent class method itself.
Using Methods Within Methods
Jan 10, 2014I have written two methods called "contains" and "overlaps". The method "contains" is to detemine whether a point (x, y coordinate) is within the surface area of a square object. The location of the square objects is determined by the location of the upper left corner of the square.The method "overlaps" is to determine whether two square objects overlap each other.
I have written these as two separate methods. However I want to change the method "overlaps", so that it uses the method "contains" within it. I.e. using a method within a method. Thereby hopefully making the "overlaps" method a bit more clear and easy to read.
Java Code:
/** Returns true of the point with the coordinates x,y, are within the square. */
public boolean contains(int x, int y){
int sx = location.getX(); //"location" refers to a square object
int sy = location.getY(); // getX() and getY() are to find it's coordinates
// "side" is the side length of the square
if (x >= sx && x <= (sx + side) && y >= sy && y <= (sy + side)){
[code]....
How To Run Two Methods At The Same Time
Jun 22, 2014Below is the main class of a project ive been working on, the goal is to start a countdown specified by the user. When the countdown reaches zero the base drops in the song that is being played. (Its not done yet) The main problem that arises is the fact that my song plays, and AFTER that, the timer starts.
Output:
Please input countdown in HH:mm:ss format.
00:00:41
Start?
Yes
The name of of the song is: Skrillex & Damian "Jr Gong" Marley - "Make It Bun Dem"
The time of base drop is: 00:00:41 //Song starts here
//Song is done
//Then timer starts
00:00:41
00:00:40
00:00:39
[code].....
Using Methods Of Interface
Feb 5, 2014I have following code. In this code CSClient is an interface. All methods of CSClient are implementaed in CSClientImpl class. Do I not need CS Client Impl imported in this code ?
How can I call getBranch() of CSClient, which is not implemented in CSClient as " this. getCsClient(). get Branch (new CSVPath(vpath), true);" ? This code works fine without any error in eclipse.
How can a method getBranch(), which is implemented in CSClientImpl class be used in this code without importing CSClientImpl ?
package com.rbc.teamsite.client;
import java.io.File;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
[code]....
Methods That Do And Do Not Return Any Value
Oct 8, 2014Write the header for a method named send that has one parameter of type String, and does not return a value.Write the header for a method named average that has two parameters, both of type int, and returns an int value.
View Replies View RelatedMethods Of Using ItemListener
Dec 1, 2014I have seen these two methods of using ItemListener. I am curios which is better and why. What are the differences?
ItemListener a;
Choice ce = new Choice();
ce.addItemListener(a);
[code]....
Put Some Of Code Into Methods
Apr 14, 2015I have had to create a text analyser. I have created the program but it is all within the main method. The specification states that I have to have at least two methods within my Program.
import java.io.*;
import java.text.SimpleDateFormat;
import java.util.*;
import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;
public class Analyser {
public static void main(String[] args) throws FileNotFoundException,
UnsupportedEncodingException {
[code]....
How To Add Methods In Attachments
May 1, 2015Java Code:
package methods;
import java.util.*;
import javax.swing.*;
public class Methods {
public static void main(String[] args) {
// TODO Auto-generated method stub
char choicee2;
[Code] .....
Arrays Outside Of Methods
Aug 22, 2014I'm working on a side project, which will eventually hopefully be a Pokedex, and I've just been going to it at the end of every chapter and using the stuff I've learned to work on it.So I just read chapter 3, which is all about variables and teaches how to use arrays.
my question is, does an array have to be declared inside a method? Because I'm trying to create an array inside a class without any methods and without the main, and I continuously get errors. Here's a quick working of my code that won't compile.
class blah {
blah a[] = new blah[7];
a[0] = new blah();
}
The error message focuses on a[0] = new blah(); Telling me the 0 should be a ], the = is an illegal start of type, so on and so forth. The program compiles completely fine if it's within a method, like this:
class blah {
void a() {
blah a[] = new blah[7];
a[0] = new blah();
}
}
Or if I have public static void main (String[]args); But I'm trying to practice working outside of main.So does an array have to be within a method,
Can Use Same Files In Different Methods
Oct 20, 2014I'm reading from one file and writing it into another.I then want to delete the first file and use the second (it will get the first files name) .My sample java file works completely fine but it doesn't work on my actual file -it looks like it populates my test file like it should but it does not delete the original. Occasionally DMap.xml won't delete either - I try and rename it and normally I get the error of 'the file is open in Java platform SE binary' so the files is open somewhere - but I thought I had closed it correctly so have I done that wrong? I have put the basic code :
public class DeleteEnvironmentsWindow extends JDialog {
String xmlFile = "c:DMap.xml";
String fromFile =xmlFile
public void removeEnvironment(){
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = null;
Document doc = null;
[code]....