Creating Instance Methods And Driver Class

May 5, 2014

Okay, so I have to create a class with instance data and instance methods.

First, BankAccount class. It should contain the following information, stored in instance variables:

First name: The customer's first name.
Last name: The customer's last name
Balance: The amount of money the customer has in the account.

It should have the following methods:

BankAccount(String firstName, String lastName,
double openingBalance)

This constructor creates a new BankAccount

public String firstName()
Returns the customer's first name
public String lastName()
Returns the customer's last name
public double balance()
Returns the customer's account balance

Finally I need to create a driver to test my class. And create several accounts and verify that the first name, last name, and balance methods work properly. This is my code below.. I don't know if I did it right.

public class BankAccount {
String firstName, lastName;
double balance;
public BankAccount(String firstName, String lastName, double balance) {

[Code] .....

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Apr 13, 2015

I am to create a Array class then create a Driver class (TestArray) to test all the methods in the Array Class. Here's the code i've written for the Array Class. I just nee developing the TestArray class.

import java.util.Scanner;
public class Array
{
Scanner sc = new Scanner(System.in);
private double[] array = new double[];
public void setArray(double[] arr) {

[Code] ...

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Mar 22, 2014

Java Code:

package Threads;
// THIS PROGRAM WILL HAVE TWO THREADS i.e. "main" AND ANOTHER THREAD (SYSTEM WILL NAME IT "Thread-0"
//THE STORY IS THAT WE WILL START Thread-0 FROM main AND LET IT EXECUTE.
//main WILL WAIT AND LET IT EXECUTE FOR 5 MINUTES.
//IF IT FINISHES ITS EXECUTION BEFORE 5 MINUTES, WELL AND GOOD;
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//AFTER INTERRUPTION, WE WILL DECIDE TO WAIT INDEFINITELY.

public class SimpleThreadsCopy {
public static void threadMessage(String s){
String sThreadName= Thread.currentThread().getName();
System.out.format("%s: %s%n", sThreadName, s);

[Code] ....

The statement against which I have written many *'s gives the following error.

No enclosing instance of type SimpleThreadsCopy is accessible. Must qualify the allocation with an enclosing instance of type SimpleThreadsCopy (e.g. x.new A() where x is an instance of SimpleThreadsCopy).

Now that a similar "error-free" code is given here, what's wrong with this piece of code and what should I do about it?

Trying to understand the error statement, I replaced the erroneous statement with

Java Code : Thread t= new Thread(new SimpleThreadsCopy().new MessageLoop()); mh_sh_highlight_all('java');

And the error got fixed. From that I understand that the inner class is just kinda a nonstatic member of the outer class and it will be accessed by the objects of the outer class only.

But then why doesn't the code in the tutorial give an error?

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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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Jul 31, 2014

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I thought I had to use this syntax :

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Mar 15, 2014

So in the code below I create an instance of my own triangle class and use one of its methods. The thing is I use one of my triangle classes methods in a method other the main method of my main program so I'm thinking it can't access it?

Any way here's the code for my triangle class
 
import java.util.Scanner;
public class QudratullahMommandi_Triangle_06 {
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private double side1;
private double side2;
private double side3;

[Code] ....

and here's the error message

QudratullahMommandi_S_06.java:46: error: cannot find symbol
{ triangle1.outPut();
^
symbol: variable triangle1
location: class QudratullahMommandi_S_06
1 error

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I am trying to get the average of 3 different fraction arrays. I made a fraction class and I made methods such as read() and average() in this new class.

package fractions;
import java.util.Scanner;
import java.util.Arrays;
public class FractionArrays {
public static void main(String[] args) {
Fraction completeFraction = new Fraction(5,6);

[Code] ....

I was wondering if there was any way to use the arrays I created in the read method in the average method. If I find that out I should be able to do it on my own. Is there a way to make the arrays public to use in different methods?

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Oct 24, 2014

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How do i access the method set_a() (through the "address" in Person) from another class which contains main() ?

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Jan 8, 2014

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Jun 30, 2014

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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?

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}
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[code]...

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Jan 6, 2015

I have two classes LightController & Circle. I need to use the LightController class to do the following:

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Sets the xPos of light to 122.
Sets the yPos of light to 162.

I am struggling to write the correct line of code to set the colour to green and set diameter to 50.

Code for the two classes below.

import ou.*;
import java.util.*;
/**
* Class LightController
* This class uses the Circle class, and the Shapes window to simulate a disco light, that grows and shrinks and changes colour.
*/

public class LightController
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/* instance variables */
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[Code] ....

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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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I am having trouble creating a driver for the following program. im new to creating interfaces and i need to make this work.

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[code]....

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I came across the below

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[code]....

I created this class "Car" (also not sure if it's correct) and need to write a driver program that creates two instances of the class Car. One must use the default constructor, and the other must use the non-default constructor. It must demonstrate the methods used in the Car class using those instances.

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[Code] ....

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May 13, 2014

Assignment:

Create a class; call it Lab4a that will have one method called pull. This method does not return anything and requires no parameters.

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-Now create a driver program, called SlotMachine, to invoke the pull method of the Lab4a class.

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-See the back of this lab for an example of the output.

This is what I have so far.

Slot machine

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[code]....

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Java Code:

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[Code] ....

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Here's a shortened version of what I have right now just based on processing the number of integers in the array (because if I can get just one method properly connected, I could figure out everything else).

Driver

import java.util.Arrays;
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[Code] ....

When I try to compile this, I currently get the "class expected" error on the count part.

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[Code] ....

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[Code] ....

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[Code] .....

The second method (getAttribute) is created by copy-paste and I also need to repeat this exercise with several other types of Enums. This seems like a waste of code however.

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This, however, doesn't compute:

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symbol: class type
location: class EnumHelper<T>
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[Code] ....

2 errors

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