Making A Rectangle - Manipulation Of Instance Variables
Sep 11, 2014
I am suppose to create a rectangle and I have created two classes; Rectangle.java and RectangleTester.Java.
So far my code for the class Rentangle.java is:
package edu.sbcc.hw2;
public class Rectangle {
private int width = 25;
private int height = 25;
public rectangle(int xcoord, int ycoord, int thewidth, int theheight) {
this.width = width;
this.height = height;
}
public int getWidth() {
return width;
So for my assignment I need two instance variables for height and width for which I have, but it says in the assignment I need methods (settings and getters /mutators and accessors that allow manipulation of my instance variables which is a little confusing. Do I put these methods on Rectangle.java or RectangleTester.java.
The same goes for the calculateArea, where am I suppose to put this?
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May 29, 2014
Write an instance method, contains, that has one explicit parameter of type Rectangle. The method should return true if every point of the rectangle determined by the explicit parameter is on or within the rectangle determined by the implicit parameter. It should return false otherwise.
This is what i did so far?
public boolean contains(Rectangle other) {
Rectangle intersect = Rectangle.intersection(this, other);
if ((intersect.left == this.left) && (intersect.bottom == this.bottom) && (intersect.width == this.width)
&& (intersect.height == this.height)) {
return true;
} else {
return false;
}
}
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Apr 7, 2014
So far in my assignment I have successfully opened a text file. However I am required to do more:
1) As each line of text (containing names and ages) is read a new Runner object is created with its instance variables set thus: ! (Runner class already created )!
- name : set directly set from the value in the file
- agaGroup : can be worked out from the given ages:
< 18 should be 'junior'
> 55 should be 'senior'
the rest should be 'standard'
2) the instance of Runner should be added to the list referenced by the instance variable runners.
I have used if statements to create the junior list, however I do not see the full list of names and ages in the variable runners as I am requested to.
I am sure there is a for loop involved somewhere but I do not know how to:
a) use the for loop in my method
add a new Runner object with the variable mentioned.
I include the code I have done so far as a file - p.s I use Bluej.
public class MarathonAdmin
{
// instance variables
private String runners;
private String age;
[Code] ....
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Oct 24, 2014
I have the following 2 classes:
class Address {
private int a;
public void set_a(int a) {
this.a = a;
}
}
class Person {
private Address address;
}
How do i access the method set_a() (through the "address" in Person) from another class which contains main() ?
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Oct 9, 2014
What is the correct way of describing the type of instance variables?
It is obvious in the case of a primitive type
Example: private int number;
The (data)type of number is integer.
What if the instance variable is an object or a wrapper?
example: private Person person;
the (data?)type of person is an object of the type/class Person?
example: private Integer number;
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Jan 8, 2014
Do 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?
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Jun 30, 2014
so, i was reading my java book and learning about objects and methods and it starts talking about Encapsulation and mentions that it's good practice to set instance variables as private and instead of accessing the instance variables directly, we should create a set method and get method to get and set the stuff we want to pass to the class containing the object...
for example, in this class, we're passing the integer 70 for object dog one and integer 8 for object dog two for the dog class... and these these 2 integers are sent to the setsize method so we're not accessing instance variable size directly.
i dont quite get it though....if we the programmer are the one deciding what size the integer is for the dog, and the setsize method takes the one.setSize(70) or (8) and puts them in setsize(int s) as s... but only to copy that integer stored in s back to private int size.... why do we even need to bother with making these two extra methods such as setSize, getSize?
in the book it says that... well what if the code gets into the wrong hand and someone writes something like one.setSize(0) then you would get a dog with size 0 which is essentially illogical. but then again, i'm the programmer, and i am the person who writes the code and passing the right integer.The reason for public and private... that part i understand... i can see why if a variable's data can get changed amidst the code during calculations and you dont want it to directly change the original variable and have it mess up the code, but this code from the book just a bad example of demonstrating the reason? since we manually pass the information ourselves and passing it to method setSize... and all setSize does is stores it in another integer, only to copy it right away to size (which is the original private variable we were tryign to protect?
Any simple code to demonstrate how the code might end up changing an instance variable and why we would want to protect it by using private?
class GoodDog {
private int size;
public int getSize() {
return size;
}
public void setSize(int s) {
size = s;
[code]...
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Jan 26, 2015
I am having some problem accessing variables from an array instance of a class. Heres what i have done;
In the main class:
Example obj[]= new Example[4];
In the main class constructor:
obj[0] = new Example(0);
obj[1] = new Example(1);
obj[2] = new Example(2);
obj[3] = new Example(3);
In the main update() method:
if(condition)
//update
In the Example class constructor:
private boolean change = false;
In the Example class update() method:
if(x >20)
change= true;
Now, i want to access the variable change from the main class, how do i do it? The 'condition' in the if statement is the condition of wether the change variable ia true or false. How do i access it?
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Mar 15, 2014
why overridden doesn't apply to variables. However, instance variables are stored inside the object.I ran below program and expected to print "two" but it gets printed "one".
class SupCont {
String s = "one";
}
class Cont extends SupCont {
public static void main(String a[]) {
String s = "two";
SupCont c = new Cont();
System.out.println(c.s);
}
}
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Mar 27, 2014
I have to create an application that deals with maps.
I first have to create the instance variables for the class.
So very simply if my hashmap is going to consist of football clubs and players. Football clubs being a string value for the key and players being a set of strings for the values. How would I go about creating the instance variable in a class for this?
I can't seem to find anything that specifically deals with instance variables and constructors for maps.
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Jun 3, 2014
From the tutorial:instance variables can be declared in class level before or after use.But the code below does not compile. Why?
Java Code:
public class MainApp {
i=5;
public static void main(String[] args) {
System.out.println("Hello World");
}
int i;
} mh_sh_highlight_all('java');
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Feb 19, 2011
I thought static methods could never use instance variables, because they wouldn't know which instance to look at.
From Head First Java, p. 284: "A static method is not associated with a particular instance - only the class - so it cannot access any instance variable values of its class. It wouldn't know which instance's values to use."
Now I was answering some mock exam questions from Cameron McKenzie's SCJA book, and I don't understand one of the options. On page 205, the last question has an option that says: "Instance variables ... are not visible in static methods, unless passed in as arguments." This option is supposed to be correct. Now... how does that work?
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Oct 9, 2014
Creating a class. Specification are given as:
Create a class called Employee that includes three pieces of information as instance variables:
-Employee ID (string type)
-first name (string type) (default value 'John')
-last name (string type) (default value 'Smith') and
-monthly salary (type double).
-No argument constructor that initializes the three instance variables. The employee id should be generated using the following process:
The employee id should be a combination of first initial, last initial and a number starting from 10001 for the first employee and increasing by one for each employee. e.g. if John Smith is the first employee then its id will be JS10001 and if George Brown is the second employee then its id will be GB10002
-Provide get and set methods for each instance variable. The set method for monthly salary should ensure that its value remains positive - if an attempt is made to assign a negative value, leave the original value.
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Jun 3, 2014
As web server has multiple threads to serve client requests in Thread Pool & to ensure Thread Safety we should not use any variables or Objects at Instance/Class level.But in case of Session Variable which one is the Best Practice as the Session object is used by all the requests to have the same Session ID.
My Code :
public class MyServlet extends HttpServlet {
private static Logger log = Logger.getLogger(ClientRegistrationServlet.class);
private HttpSession session; /* This is used at Instance Level*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
[code]....
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Mar 7, 2014
I've Parent and child(extends Parent) class To initialize the constructors, I'm injecting from google.juice#injector. Let me show the code,
Parent.class
public class Parent{
private Animal animal;
@inject
Parent(Animal animal){
this.animal = animal;
[code].....
When I do this, ClassCastException is happening. Why is it so? Is there any way to convert instance of parent to child instance.
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Oct 25, 2014
I currently have an on going project of making a gameengine and am currently doing a lighting engine. How to create simple algorithm of explain to me the concepts of creating a algorthm to do a task, like explain how to get the hue saturation and brightness. This preferably needs to be done in java for me to copy the code but as long as i have a concept to go by I could probably translate the code over so it's not to much of a problem.
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Sep 15, 2014
I'm currently starting my thesis where my Project will involve creating a diff and merge tool for simulink slx files. These are built using several xml files, a png and sometimes some other data files. One can get to these files by changing the file extension to zip.
I am a bit troubled by this since I want to be able to handle all these files simultaneously and hence need to do this automatically when choosing the slx file.
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Mar 9, 2014
"Object contains data and code to manipulate that data."
Is the statement right ?? as far as i know object only contains copy of instance variables.
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Nov 21, 2014
I have a jpeg that I need to print a border around. My plan was to take the jpeg and throw it on top of a second image that is a few pixels bigger in each direction. Currently, my code prints the image with a white border on the right and bottom sides. Is there a way to print the border on all sides, and maybe even make it a more distinct color? I am not allowed to use graphics. I can only manipulate pixels. Here is the basis of my code.
public class MyArt
{
private Picture image;
/**
* Create an Art object using the jpg or bmp at the indicated location
*/
public MyArt(String filename)
{
image = new Picture(filename);
[code]....
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Apr 17, 2014
I have a string and i need to do some manipulation with that. I have tried couple of things but not sure if those are feasible or not. Here is the situation:
uid=aa,bb,ou=people,cn=administrativeldap,cn=punit.punit.a-12-m020.20,o=ttt
I want the value of uid from this string, actually it's user id.
This particular string i want :: aa,bb
Things which i have tried:
I was trying it in this way string start with uid and ends with ou, but in this case user name itself can have ou, so in that case it breaks. Another approach i was thinking of is splitting the string by = which gives me aa'',bb,ou at first position and then i will again split this string to remove ,ou. but i am not sure if this approach is good or not?
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Apr 14, 2014
I need to create an java 2D application for the manipulation of image. I saw the JAI library but it can not install it properly, I also copied the jar but I can not find the solution. How can I do? there is a replacement for JAI? what other libraries can I use?
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Jan 23, 2015
I have to write a program that asks the user to enter the name of their favorite city and use string variable to store the input. The program should display the following:
-The number of characters in the city name
-The name of the city in all uppercase letters
-The name of the city in all lowercase letters
-The first character in the name of the city
However, I can't seem to get past the following errors;
Programming Challenge #12.java:37: error: variable cityFirstChar is already defined in method main(String[])
char cityFirstChar = city.charAt(0);
^
8 errors[CODE
----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.
[/CODE]
My code is as follows:
import java.util.Scanner;
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
[code]....
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Nov 20, 2014
I am working on a project using pictures and am having some trouble. My assignment is to take a jpeg, and reflect it(over an imaginary x-axis so to speak). As this is my first time working with images, I am very lost. My approach was to take "pixel 0" and have it swap places with "pixel max". Theoretically, I believe I would only need to do this for the first 50% of the pixels, as each flip works on 2 opposite pixels. With my code thus far (the reflect() method), I print the left half of the image. Note: I must use pixel manipulation. I cannot use graphics.
public class MyArt
{
private Picture image;
/**
* Create an Art object using the jpg or bmp at the indicated location
*/
public MyArt(String filename)
{
image = new Picture(filename);
[Code] .....
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Feb 18, 2014
I do have a quick question about string manipulation. You see I've been given a simple exercise that involves asking the user to input a number between 1,000 and 999,999 and displaying the result. Simple enough, but the caveat is that if the user keys in the comma, say 24,000 instead of 24000 for example, the program is not to display the comma. I don't see how to do this without an 'if' statement. The book says the 'if' is not necessary but does offer this hint: "Read the input as a string. Measure the length of the string. Suppose it contains n characters. Then extract the substrings consisting of the first n-4 characters and the last three characters."
What good is n-4 going to do if the string's lengths varies?
Here's what I have written thus far:
import java.util.Scanner;
public class P13
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
System.out.print("Please enter a number between 1,000 and 999,999: ");
[Code] .....
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Sep 29, 2014
I am attempting to use JLists to complete a program that models how operating systems manage processes. A quick synopsis of what it is supposed to do. Each process is to have a priority level (I chose to do 1 -3 with 3 being the most important) and there are supposed to be three lists. One for ready processes, blocked processes, and a running process.
My issues:
1) when I block a process it does indeed switch lists but when it is copied into the blocked list it pulls the element number instead of what the actual process number is. For ex: Say the ready list has 5 processes / I delete 2 / Leaving process 1, 2, 5. When I block 5, it gets registered in the blocked list as process 2.
2) I can't figure out how to give a label to each of my scroll panels (JLists) to signify which box is ready / blocked / and running
3) My switch button - I have commented in what I need to do but don't know how I am going to do it.
Below are my files:
Main
import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;
import javax.swing.JFrame;
import javax.swing.JTextArea;
public class PQueue {
public static void main(String[] args) throws InterruptedException {
[Code] ....
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Oct 1, 2014
I'm playing with vectors for the first time... What I'm trying to do is to allow a user to input one or more integers and store them in a vector for manipulation later on in the program... Here's the portion of the program I'm working with:
Java Code:
package com.itse2317;
import java.util.*;
public class VectorTest
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
[code]...
My question is this: Is there any way to move from inputting integers to printing them, without entering a non-integer (for example, hitting enter)? I looked at the API for the Vector class, and either I'm not thinking about the problem the right way to be able to find an answer, or it's just not there.
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