Difference Between Object Reference And Object?
Dec 1, 2014difference between object reference and object
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Equals Method - Take Object Reference And Return True If Given Object Equals This Object
Mar 28, 2014Create an equals method that takes an object reference and returns true if the given object equals this object.
Hint: You'll need 'instanceof' and cast to a (Geocache)
So far I have:
public boolean equals(Object O){
if(O instanceof Geocache){
Geocache j=(Geocache) O;
if (this.equals(j)) //I know this is wrong... but I can't figure it out
return true;
}
else return false;
}
I think I have it correct up to the casting but I don't understand what I'm suppose to do with the this.equals(). Also I'm getting an error that I'm not returning a boolean... I get this all the time in other problems. I don't get why since I have to instances of returning booleans in this. "returns true if the given object equals this object" makes no sense to me. I assume the given object, in my case, is 'O'. What is 'this' object referring to?
Inheritance Relationship Between Type Of Actual Object And Object Reference?
Apr 15, 2014For example I create an object like this:
BankAccount b = new SavingsAccount();
Now lets say that I want to access a method 'addInterest()' that is in the 'SavingsAccount' class I would have to do: '((SavingsAccount)s).addInterest();'
The question I have is why do I have to cast 'b' to SavingsAccount? Isn't the actual object reference of 'b' already an instance of 'SavingsAccount' class? How does the 'BankAccount' affect the object itself? I'm really confused as to what class is truly getting instantiated and how BankAccount and SavingsAccount are both functioning to make the object 'b'.
Object Reference Variable Unwilling To Be Reset To A Different Object Type
Nov 6, 2014I don't understand why the object reference variable 'a' cannot be recast from a thisA object reference to a thisB object reference.Is it the case that once a reference variable is linked to a particular object type then it cannot switch object types later on.I am facing the Java Associate Developer exam soon and I am just clearing up some issues in my head around object reference variable assignment,
class thisA {}
class thisB extends thisA { String testString = "test";}
public class CastQuestion2 {
public static void main(String[] args) {
thisA a = new thisA();
thisB b = new thisB();
[code]....
How To Reference The Object
Jan 27, 2014I am doing a Junit test case, but I keep having issues with AssertEquals ( object expected, object actual). I don't know how to reference the other actual object so that it can compare to the expected.
public void add (Distance d) throws CustomException
{
//I can also convert feet to inches and add all inches together and then divided inches to feet and inches
Distance result = new Distance();
int newFeet = this.feet + d.getFeet();
int newInches = this.inches + d.getInches();
if(newInches > 11)
{
newFeet = newFeet + (newInches/12);
[Code]...
How To Reference Object Created In One Class From Another
Oct 30, 2014I have started working on a little project in my free time. It is just a simple text rpg that runs in a counsel window. I have 5 files each file contains 1 class.
public class SomnusCharacter {
private String gender = "";
private int age = 0;
private String race = "";
private int level = 0;
private int xp = 0;
[Code] ....
The chain of events right now is:
1. MainMenu is run
2. If user inputs n CreateCharactor is run
3. User inputs name, age, ect in SomnusCharacter object made in CreateCharacter
4. Intro (just rough demo for testing purposes) is run
5. If user inputs m Menu is run
6. Menu calls and prints out all the information from the object made in CreateCharacter
Step 6 is where I am having my problems. How can I reference (lets say the SomnusCharacter object made is called player) player from my Menu class? I know that if I made a new character that it would just create another SomunsCharacter object with the default values again.
Class That Needs To Be Copied Also Contains Reference To Other Object
May 22, 2014I read somewhere : "Java use clone() method of Object class to copy content of one object to the other. The problem will arrive if the Class that needs to be copied also contains reference to the other object."Not able to understand the second line.
View Replies View RelatedDifference Between A Class And Object
Jan 29, 2014I have finished a Java 101 class but the most we did was create a gui for a timer program. I figure I need more training and every book I pick up wants to teach me hello world and the difference between a class and object again.
View Replies View RelatedMethods Checked Based On Reference Not The Object?
Jun 15, 2014Check out the following basic code (assume that dog has a method called bark):
Dog d = new Dog();
Object o = d;
o.bark(); // error
But why? Isn't o just a pointer to a memory address which has the dog object? If so, why can't the compiler see that the object has a method called bark? Or, to ask the question another way, why is Java designed to check the object reference to see if the method exists instead of the object itself?
Cannot Assign Generic Object Reference To Similar Type
Jul 26, 2014I have the following code:
public class CollisionManager<T> {
private boolean collision = false;
private T mainEntity;
public <T extends Entities> void handleCollision(T mainEntity, T secondEntity){
this.mainEntity = mainEntity; // This is illegal.
}
}
Why "this.mainEntity = mainEntity" is incorrect and also show me the correct way to achieve this?
The error I am getting is "Type mismatch: cannot convert T to T"
Get Object Strings To Print In List So That User Can Select That Object To Manipulate Its Attributes
Oct 7, 2014I am new to Java and have read books, the Java docs, and searched the Internet for my problem to no avail. I have an Array of objects that contains strings. How can I get the object's strings to print in a list so that the user can select that object to manipulate its attributes? For example, the user can select "Guitar 1" from a list and manipulate its attributes like tuning it, playing it, etc. I have a class called Instruments and created 10 guitar objects.Here is the code:
Instrument [] guitar = new Instrument[10];
for (int i = 0; i < 10; i++) {
guitar[0] = new Instrument("Guitar 1");
guitar[1] = new Instrument("Guitar 2");
guitar[2] = new Instrument("Guitar 3");
guitar[3] = new Instrument("Guitar 4");
guitar[4] = new Instrument("Guitar 5");
guitar[5] = new Instrument("Guitar 6");
[code]...
Swing/AWT/SWT :: How To Move A Object And Make Object Shot Laser
Mar 27, 2015can a keyevent in java make the space ship and the laser too ?
View Replies View RelatedType In A Name And It Will Search Through Each Object And Print Back Corresponding Object Info
Nov 19, 2014I am trying to get this to where I can type in a name and it will search through each object and print back the corresponding object info.
Java Code:
import java.util.Scanner;
public class MyPeople {
public static void main(String[] args) {
Person[] p = new Person[] {
new Person("Chris", 26, "Male", "NJ", "Single"),
new Person("JoAnna", 23, "Female", "NJ", "Single"),
new Person("Dana", 24, "Female", "NJ", "Single"),
new Person("Dan", 25, "Male", "NJ", "Single"),
new Person("Mike", 31, "Male", "NJ", "Married") };
[code]....
Create Object Deriving From PrintingClass And Use That Object To Print Text
Apr 9, 2014Task:The main method of the class Things below creates an object called printer deriving from the class PrintingClass and uses that object to print text. Your task is to write the PrintingClass class.
Program to complete:
import java.util.Scanner;
public class Things {
public static void main(String args[]) {
String characterString;
Scanner reader = new Scanner(System.in);
PrintingClass printer = new PrintingClass();
System.out.print("Type in the character string for printing: ");
characterString = reader.nextLine();
printer.Print(characterString);
}
}
// Write the missing class here
Note: In this exercise the solution is part of a conversion unit where many classes have been declared. Because of this the classes are not declared as public using the public attribute.
Example output
Type in the character string for printing: John Doe
John Doe
My Class:
class PrintingClass {
public void print(){
System.out.println(characterString);
}
}
Display Properties Of Each Object Instead Of Object Array List Itself?
Mar 23, 2015If I set a Jlist to contain an array of objects, how can I display properties of each object instead of the object array list itself. Ex:
Instead of:
Person1
Person2
Person3
display values such as each person name within the Jlist:
Mike
Paul
Andrew
Searching For Object In Linked List Then Removing The Object
Nov 19, 2014I have just started working with linked lists. I have a linked list of Objects and I want to be able to search for a specific object. But currently my code continues to return false. Also how would I go about removing the first index of the linked list.
public static void main(String[] args) {
LinkedList<Cookies> ml = new LinkedList<>();
int choice = 0;
while (choice >= 0) {
choice = menu();
[Code] ....
Practical Use Of Multiple Object References Pointing To Same Object
Dec 27, 2014I am reading Head First: Java and got to Object References. In the book I got a little bit confused on what happens when two object reference's point at the same object so I wrote a small crude test, the below code. This of course clarified what happens but what I am interested in knowing is in what circumstances would you want to have two separate references for the same object when you could just use the original? Eg. v1
class ObjectValue{
int objVal = 1;
}
class ObjectValueTestDrive{
public static void main(String [] args){
// "Value of v# should be" refers to if it copied the given object values, instead of referencing the same object
ObjectValue v1 = new ObjectValue();
System.out.println("Value of v1 should be 1:" + " "+ v1.objVal);
[code]....
Anonymous Object - Can't Understand One Time Usage Of Object
Aug 18, 2014Explain anonymous objects with example clearly...i read some where anonymous objects advantage is saving memory...it is benificiable when there is only one time object usage in our program..i can't understand one time usage of object ....i know anonymous objects but i don't know in which context we use them in our programs...i did the anonymous object program with my own example but i can't differentiate this one with normal object..i'm providing my own example below
//anonymous object
public class anonymous {
int x=10;
int y=25;
void display()
{
System.out.println("anomymous");
[code]....
Swing/AWT/SWT :: Have Object Notify Main Object
Jan 15, 2015What I want to do is have a label that is updated whenever an object gets some new, relevant data.The way you do it in Java looks different from the way we do it in Objective-C. In Objective-C, we have what's known as a protocol. An Objective-C protocol is almost exactly like a Java "implementation." In Obj-C, if I want the user to see the address of where he is, I can have an object that gets the information and invokes a view controller's method; at that point, the view controller would then take the data passed to it and display the data in a label. However, the view controller is an instance of a subclass of the bundled view controller class.
View Replies View RelatedSwing/AWT/SWT :: Pass Object With Properties To Another Object
Jun 11, 2014I am trying to find either some references to point me on the right track with passing an object with all of it's properties still in tact after it's been created. Currently I am trying to do this through an interface but it seems to just create a new object everytime without the properties. Example below :
import java.util.ArrayList;
import java.util.List;
public interface TPerson{
//public Person p = null;
}
class Thrower {
Person p;
[code]....
When I implement the interface on the other objects as soon as I call the setP method shown above it seems to just create a new one even though I pass the object to the method I want to use.
Calling Object Method From Another Object
Oct 26, 2014I've been trying to learn Java for the last 36 hours or so (after applying for a HTML/CSS job saying "Java knowledge preferred"), and decided to experiment a bit making a graphical tic-tac-toe game. I eventually managed to get that done and it's working. Working code below:
[Java] tic tac toe 1 - Pastebin
So, it works to an extent, however, the way I am capturing which cell is selected seems very sloppy, and would not work if the cells weren't squares or rectangles. So I made a copy of the project and restructured it adding the mouse event to the cells, but now I can't get JComponent to repaint. New code below:
tic tac toe 2 - Pastebin
Curiously, clicking triggers the action for all 9 cells, but I presume it's because I haven't bounded them making it think I've clicked all 9 simultaneously.
What I've tried:
Make the Cell class extend the game class and call this.repaint()- causes stack overflow.
Calling Game.GameState() within the cell clicking event and making that function static - compiler doesn't like calling repaint() inside a static function.
Making another class to make a clone of the Game object and then refresh- was never going to work....
Should Instantiate New Object In Value Object Class?
Sep 22, 2014I have a value object class and it has the below member
XMLDocument request = null;
Should I instantiate it in the VO class as
XMLDocument request = new XMLDocument();
or leave it null and let the calling program instantiate it?
What's the proper way to do it for Value Object classes in java ?
Storing Custom Object In SQLite DB / Serializing Custom Object?
Jul 13, 2014I have this arraylist off a custom object that looks like this witch also contains a list off custom objects
package holders;
import java.util.ArrayList;
public class ManufacturingJobHolder {
private String name;
[code]....
Populating ArrayList Object With Nested ArrayList Object
Jul 8, 2014I have stumbled onto a problem with ArrayLists (not sure if nested ArrayList objects would be a more accurate description) ....
As simply put as I can describe it, I have an Inventory class which creates an ArrayList of a Product superclass, which has two subclasses, PerishableProduct and ItemisedProduct.
By default, the program is meant to have a starting inventory, which is why I have added them in the constructor
public class Inventory {
private List<Product> products;
public Inventory() {
addProduct(new Product("Frying pan", 15, 20));
addProduct(new PerishableProduct("Apple", 5.8, 30, 7));
addProduct(new ItemisedProduct("Cereal", 5.8, 0));
// this is where I am having problems. Wanting to add
// objects to the ItemisedProduct's ArrayList for cereal.
}
Within the ItemisedProduct subclass is yet another ArrayList which is meant to hold serial numbers.
public class ItemisedProduct extends Product {
private ArrayList<String> serialNumbers = new ArrayList();
public ItemisedProduct(String name, double price, int qty) {
super(name, price, qty)
[Code] .....
My problem is that I do not know how to populate the serialNumbers ArrayList from the Inventory class' constructor. Because technically, quantity is defined by how many serial numbers are created.
Declaring Object Using Interface Implemented By Its Class Vs Declaring Object Using Class
Apr 8, 2014Suppose you have a generic Dog class of the pet type that implements a DogInterface of the pet type. What is the difference between;
DogInterface<pet> Rex = new Dog<pet>();
and
Dog<pet> Tye = new Dog<pet>();
In what situations might you want to use Rex instead of Tye?
What Is A Class Object Not Class Named Object
Mar 24, 2014"You might wonder what happens when a static synchronized method is invoked, since a static method is associated with a class, not an object. In this case, the thread acquires the intrinsic lock for the Class object associated with the class. "What is a Class object associated with a class. Google search rather finds material about the Object class.
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