I have this piece of code I wrote a while ago to test something. The issue is accessing a private field of Base class in Base but of a Derived object.
Here is the code:
class Base
{
private int x;
public int getX()
[Code]....
The commented code does not work but casting d to Base does.
Forgot to mention that the compilation error is that x has private access in Base.
When we say derived class that means copy of base class plus subclass specific implementations. But when it comes to private members it cannot be accessible in subclass scope. Does it mean byte code generated for subclass doesn't has byte code of private members of super class ?
View Replies View RelatedI came across the below
1) When a variables are declared "Private" How should it be accessed from the driver class ? Sometimes i get an error in driver class saying "your variable is declared Private" why am I getting this error ...
The document says "Private" declared variables should be accessed only through methods. What does that mean.
can we pass private final class object to another class constructor?
View Replies View RelatedI'm working on this program for a class to create objects of a commissioned employee and union employee. Everything seems to work ok, but when I run my final pay calculation, one of my getter functions will not pass the variable for the pay into a class specific variable called check. here is the code in this function.
public void finalPayCal_U() {
setweekPay();//calculates weeks pay under 40 hours, stored in getweekpay
check = getweekPay();
if(getHours() > 40){
check = check + (1.5 * (getHours() - 40) * getRateOfPay());
}
check =- Dues;
}
}
The issue lies in check = getweekPay();
I thought this was a legal move, but I can't get it to work. It doesn't come back with anything more than 0 any time I run it.
All of these functions are out of the base class, employee (this function itself lives in the derived union class)
public void setweekPay() {
if (hours <= 40) {
weekPay = hours * rateOfPay;
} else {
weekPay = 40 * rateOfPay;
}
}
When I run, this function works as it returns the value when i print it to test.
however, when I do the part that says check = getWeekPay() above, it doesn't change the check variable. The only thing I have on the check variable is the dues taken out of it at the end, so it ends up being a negative number.
I have a similar problem with the other derived class's check variable. Both classes have the same variable as private but one is check the other checkC.
Design a class named Person and its two subclasses named Student and Employee. Make Faculty and Staff subclasses of Employee. There is also a MyDate class as explained below. A person has a name, address, phone number, and email address. A student has a status (freshman, sophomore, junior, or senior). Define the status as an integer which can have the value 0 (for "Freshman"),
1 (for "Sophomore"),
2 (for "Junior"), and
3 (for "Senior"),
but don't allow the status to be set to any other values. An employee has an office, salary, and dateHired. The dateHired is a MyDate field, which contains the fields: year, month, and day. The MyDate class does not explicitly inherit from any class, and it should have a no-arg constructor that sets the year, month, and day to the current year, month, and day. The MyDate class should also have a three-argument constructor that gets three int arguments for the year, month and day to set the year, month and day.
A faculty member has office hours and a rank. Define the rank as a String (for values like "Professor" or "Instructor"). A staff member has a title, which is also a String. Use data types for the fields as specified, or where one is not specified, use a data type that is appropriate for the particular field. Write a test program called TestEveryone.java that creates a Person, Student, Employee, Faculty, and Staff object, and invoke their toString() method (you don't need to call the objects' toString() method explicitly).
Note: Your MyDate.java class is the object class that your dateHired field is created from in the Employee.java class.
Do not use the Person, Employee or Faculty classes defined on pages 383 and 384 of the book. Create new ones.Here is the code I have so far concerning the employee and MyDate.
public class Employee extends Person {
private String office;
private double salary;
//private MyDate dateHired;
//7 argument constructor for employee
public Employee(String name, String phoneNumber, String email, String address, String office, double salary /*MyDate dateHired*/) {
super(name, phoneNumber, email, address);
[code]....
I want to know is there any way we can call parent class method using child class object without using super keyword in class B in the following program like we can do in c++ by using scoop resolution operator
class A{
public void hello(){
System.out.println("hello");
}
}
class B extends A{
public void hello(){
//super.hello();
System.out.println("hello1");
[code]....
I have a situation where I have 2 classes and an array of objects which are causing me trouble.
The object type is one I have created - it is made from a class which is neither of the 2 classes I previously mentioned.
The array is created and occupied in Class1 and the problem arises when I try to reference one of the element from Class2.
At first I forgot the the array would be local to Class1.main so I made the array a global variable using:
Java Code: public MyObjectType[] myArray; mh_sh_highlight_all('java');
Then I tried accessing an element (2) from Class2 using:
Java Code: Class1.myArray[2] mh_sh_highlight_all('java');
However I get errors saying that I can't access the static variable from a non-static context.
I understand a little bit about static and non-static objects/methods but don't know how to fix this. Do I need to include "static" in the array declaration?
I think the following code should trigger a compiler error.
public final class IPoint3D {
private double x;
private double y;
private double z;
public IPoint3D(double x, double y, double z)
[Code] .....
1. I want to use a scanner in my child class so that I may populate my parent class. It won't allow me something about scanner constructor. I posted this issue second which is my child's method Tests
2. I can't call my addTestsAnswers method from main to my child class but can call my child's display method from main.
import java.util.Scanner;
public class Tests extends Assessment{
private String q;
private String a;
private int userInput;
Scanner scan = new Scanner();
Scanner scn = new Scanner();
Scanner u = new Scanner();
public void addTestsAnswers(){
[code]....
I am trying to create a method for my "ticketmachine" object that counts ticket objects in an arraylist of "ticket" objects with a specified field "route". The method works if i change the field type of the ticket class to public, however according to the homework task "route" of the ticket class needs to remain a private field.
Here is my code for the method.
public int countTickets(String route) //HAD TO CHANGE Ticket class FIELD "ROUTE" TO PUBLIC!!!!
{
int index = 0; //returns the number of Ticket objects in the machine with the specified "route".
int ticketCounter = 0;
while (index < tickets.size())
[Code] ....
Is my general approach to the problem wrong? also is there a way to access a private field?
So i'm writing a for loop to convert any number entered to base 10 with any base provided as well. My code does not work because I need a way to reverse the code order, so the new number is printed correctly with the given base. My code so far:
public static void main (String[] args) {
Scanner kb = new Scanner (System.in);
System.out.print("Enter a number :: ");
int numOriginal = kb.nextInt();
System.out.print("Enter a base :: ");
int base = kb.nextInt();
[Code] .....
newBase has a problem with how it calculates the new number, looking for correct newBase code for conversion?
I am writing a program to convert a base 10 integer to any base 2-16. Here are the terms:"The method is to convert the decimal value the user selected into whatever base the user selected and print the converted value one place value at a time by using an index into an array of characters 0-9 amd A-F that is initialized to contain those characters.In the method you will find the largest place value (i.e. power of the base) that will divide into the decimal number.
Then you can set up a loop that will operate from that power down to and including the 0th power to determine how many times each place value goes into the decimal number. Using the loop counter, index into the character array to print the character that corresponds to the quotient number and then subtract the product of the place value and the quotient from the decimal number. With the power (loop index) decreased, repeat until you finish the 0th place value. Here's what I have so far:
import java.io.*;
import java.util.Scanner;
public class ConvertIt
{//start program
public static void main(String[] args)
{//start main
Scanner input = new Scanner(System.in);
System.out.println("Enter a positive integer from 0 to 10000.");
int number = input.nextInt();
[code]...
I want to use my given code as base class
Java Code:
public static void file(String[] arg) throws IOException{
BufferedReader in;
String line;
try{
System.out.println("Reading word");
in =new BufferedReader(new FileReader("inp.txt"));
[Code] .....
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]...
We were asked to do a program in java that could convert Base n to Base m. and im really having trouble with it.
View Replies View RelatedI had to write a program for class to request user input for base salary, number of years worked, and total sales. Then use the data to find out the employee's paycheck when including a bonus. I have a few issues with the code, as I have one bug, then it won't calculate anything. what I'm missing?
package chapterone;
import java.util.Scanner;
public class Examplelab {
static Scanner console = new Scanner(System.in);
public static void main(String[] args){
double baseSalary;
double noOfServiceYears;
double totalSales;
[Code]....
Scanner in = new Scanner(System.in);
ArrayList<rand> selectedRand = new ArrayList<Rand>();
selectedRand.add(new Rand(in.nextLine()));
I have created the most minimal code for creating an array list. I was wondering what the basic syntax of accessing objects methods that are within an Array List. So if I was to trying and get a method such as [.returnValue,] how would this look within a Rand object that is declared in a Array List Since you cannot simply declare a new Rand object and say:
newRandObject.returnValue();
And you must go through the actual slotted portion of the array list. I have searched the web and my text book for an example however none are provided.
I have a project where I must sort a collection of songs by a number of fields: year, rank, title and artist. in the project, we must use certain methods and we cannot add others without getting marked down. Here are the specific requirements:
Sorting
The -sortBy option will cause the output to be sorted by a particular field. If this option is specified, the output should be ordered according to the field named. If there are ties, the tied songs should appear in same order in which they were in the input file. If no -sortBy option is specified, the output should maintain the order of the input file.
public void sortYear()
Order the songs in this collection by year (ascending).public void sortRank()
Order the songs in this collection by rank (ascending).public void sortArtist()
Order the songs in this collection lexicographically by artist (ascending, case-insensitive).public void sortTitle()
Order the songs in this collection lexicographically by title (ascending, case-insensitive).
Here is the relevant code:
SongCollection Class
Java Code: import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.*;
[code]....
public class BookExamples {
String title;
String genre;
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println("Hey");
[code]...
Eclipse gives me an error for b1.genre = "hey"; saying "Syntax error on token "genre", VariableDeclaratorId expected after this token". I am learning from a HeadFirst Java book that is all in Java 5.0 version which may be part of the problem.
I'm working on a project that contains multiple classes. Each class contains and must contain only PRIVATE variables. Here's my issue. When my test code calls for a new instance of "StudentClass" as so:
StudentClass studentClass = new StudentClass(offeredClass.getClassIdNumber(),
offeredClass.getClassName(),
offeredClass.getClassroom());
The corresponding constructor won't let me initialize it's variables because they are declared private within another class, as shown here:
StudentClass (float classIdNumber, String className, Classroom room){
this.classIdNumber = classIdNumber;
this.className = className;
this.room = room;
}
When getClassName, getClassroom, and getClassIdNumber are passed to a toString() method elsewhere in my test code. the output is returned just fine. When passed through the StudentClass, I'm getting Null across the board.
I'm not new to java but i'm not able to solve the following issue: I have a class
public class Localizzazioni implements java.io.Serializable {
private <complexType> id;
public getId().......
public setId().....
The complexType is a class defined in the code somewhere. Now I want to access it in another class I have
Set localizzazioni = new HashSet(0);
localizzazioni=opere.getOiLocalizzazioneOperas(); -- this object give an object of tyoe HashSet
for(Object object : localizzazioni) {
object.get......... // i cannot use any method defined in the class Localizzazioni
}
Why I cannot write inside the for object.getId() and using it?? In other word how i can access the element contained in the object?? the object is an iterator of type Localizzazioni . The class Localizzazioni has some method but i cannot use them? why ....
I got a strange (!?) behavior using an FXML annotated object ...
Consider the following:
You got an app with FXML build UI.
There is a button called connectB which is @FXML annotated...
In the initialize method of my app I disable this button.
After the startup of my app I want to connect to a DB ...
Therefore I use an Task<Void>
I put everything together in one class ( the main application class )
Here is the code...
public class MainApp extends Application implements Initializable{
// ... several other objects
@FXML
private Button connectB;
@Override
public void initialize( URL location, ResourceBundle resources ) {
connectB.setDisable( true );
[Code] .....
The connectB is not null in the initialize method but later in the task class ....
Java Code:
import java.util.Scanner;
import java.util.ArrayList;
public class Problem1
{
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
ArrayList<String> list = new ArrayList<String>();
[Code] ....
There is an error and says that my ArrayList has private access. I can't figure out how to fix it.
The code runs but when I enter "Quit", the program just stops. The arraylist isn't printed out?
When creating a class with a constructor, why does one have to create private variables (attributes) to be used as parameters by the object? The object's parameters will be set to be exactly equal to the private variables (attributes), so what is the point of having the private variables (attributes) Why are both private variables (attributes) and parameters needed when they are set to be equal each other anyway?
View Replies View RelatedI've tried a couple ways to do it, and they don't work. I'm aiming for functionality like I got with the regular for loop, but from an enhanced for loop. Is this simply beyond the scope of an enhanced for loop, or am I just not getting the right syntax?
TestObject to1 = new TestObject("first", 11);
TestObject to2 = new TestObject("second", 12);
TestObject to3 = new TestObject("third", 13);
TestObject to4 = new TestObject("fourth", 14);
TestObject to5 = new TestObject();
List<TestObject> testList;
testList = new ArrayList<TestObject>();
[code]....
The TestObject class is simply an int and a String, with getters getInt and getString. It all works fine with the regular for loop.
edit: I should probably mention that I know what I have in the enhanced for loop now will only display the class name and the hash. I've tried adding the .getString and .getInt, and tried a few other ways to make it work. I just reverted to this because it compiles and runs