I'm writing a simple program in which I have a super class Person, inherited by the subclasses Customer and Employee (they inherit the variables ID, name and surname).
Java Code:
public class Person {
int id;
String name;
String surname;
public Person () {
[Code] .....
However the problem is here: when I try to get the variables ID, name and surname through my main class, they fail to return (0,null,null). Why is this? I have get-Methods in my subclasses which should return the super variables, but they are not.
Java Code:
public String getUser() {
return username;
}
public String getName() {
return super.name;
} mh_sh_highlight_all('java');
what does super(); do in the following method, I understand its uses to access variables belonging to the superclass but i am unsure of what that one line does. Here is a sample constructor..
public CreditCard() { // fill in the default constructor and use the super call super(); id = "000000"; year = 0; }
how to get access from variables in a super class or a subclass. Here is what I got:
1) I have a super class that is in Jar file, I created a link in Eclipse, I know that the link is created correctly, I am going to concentrate just in one variable, so I don’t have to put all the code here firstName; in the super class(the one that is define in the path)
public class CommissionEmployee { // Field descriptor #6 Ljava/lang/String; private java.lang.String firstName;
Take a look at this screenshot... my java integrated devlopment envirnment is telling me I have a null pointer on a line with three variables ALL which were initialized.
I thought a null pointer was called when a variable doesn't get initialized.
Edit: Here is the java file and resources being used: [URL]
I am very Java illiterate and I need to know how would i set all the variables in the first class to null or 0 to make a new method to clear everything.
import java.util.Arrays; import java.util.Scanner; public class studentMethods { private double totalScore; private int count;
I want to return the Range of Variables from a Function as follows.
X will be within 3 to 5
Y will be with in 10 to 15.
Z will be with in 22 to 34.
and so on...
I have extracted the variables and their ranges. But not sure which data Structure or class should be used to return it from the Function. Will Hashmap Works? I use Key of Hashmap to denote Variable and Value field as 3 for X, But how can I indicate 5 which is the Max value X can take?
I want to use a method, which takes for example an int and also returns an integer. For example, if the the given integer is strong return a, if it is notstrong return b. How would you write that in a Code?
I want to use that in a more general way. I want to give a method mlong the value X of the type date and let it return an int. Type date consists of 3 int, one of them is the int month.
mlong should return an int depending on the X.moth. at the moment my code looks like this:
// File1: public class date { public int day; public int month; public int year; }
// File 2: public class monthlength { public int mlong(date X) { int t; t = X.month; if (t == 1 || t == 3 || t == 5 || t == 7 || t == 8 || t == 10 || t == 12) { return 31; } if(t == 4 || t == 6 || t == 9 || t == 11) {return 30;} } }
I have inherited some code that is supposed to work just fine. The trouble is that when everything is rebuilt on my desktop, the projects crash. They all seem to crash at one particular part of code.
I pass it a string and the "getResource" or "getContentClassLoader" is failing.
[URL] ....
I guess one way to tackle this is to break it apart into segments.
I have inherited some code that is supposed to work just fine. The trouble is that when everything is rebuilt on my desktop, the projects crash. They all seem to crash at one particular part of code. I pass it a string and the "getResource" or "getContentClassLoader" is failing.
As part of a homework assignment in my 1st Java Class, I am creating my own Circular Generic LinkedList and Array class. My class uses the Queue Interface Extends Iterable but I am creating my own methods to work with. For the most part, I believe I have been successful in creating the class aside from one method. That method is the Iterator<E> iterator().
/** * Return a fail-fast iterator, which throw a java.util.ConcurrentModificationException * if the client modifies the collection (via enqueue(...) or dequeue()) during iteration. */ @Override public Iterator<E> iterator() {
I don't understand how an iterator, let alone a "fail-fast" iterator ties into my project. I've spent hours reading up on a way to imploy my own generic fail-fast iterator but to no avail.
I feel like I could come up with some workable code if I knew what the point is to useing a user-defined, non Java Library iterator is to do.
As well, does throwing a ConcurrentModificationException require a try and catch block?
I have a task of returning US holiday based on the given date and this utility will be used in a multi thread environment. I have written as below, how to know if my code breaks at any given point by multiple threads
I tried to test this with few concurrent threads, and noticed that the DB call is made for the very first time or when the year being requested is not same as the cached year. But I wanted to see, if this is properly synchronizing and would not fail in any case. My intention is to make a singleton HolidayCalendar, and also synchronized well enough so that every thread using this class gets the required data without blocking each other.
public class Test { public static void main(String[] args) { Car c = new Car(); c.setInf("toyota", "red"); System.out.println("name: "+ c.brand + " colour: " + c.colour);
[code]....
Why do I get the result brand null, colour null? I know what null means but what am I missing here?
Set<? super TreeMap> s = new HashSet<SortedMap>();
SortedMap<String,String> sm = new TreeMap<String,String>(); TreeMap<String,String> tm = new TreeMap<String,String>(); s.add(sm); //This fails s.add(tm);
Why does adding sorted map to a Set that allows ? super TreeMap and instantiated as such fail?
I want to make an application and must use strategy pattern my idea is to create a super class in this case Movie Player and three sub classer and they'll komminesera with each other using strattegy pattern, one of the sub classes is Button Panel and I want to add it to Movie Player and it was to be its child,so how can I add the butt panel to Movie Player and it shall be its children?
How do i take input values for TwoDPoint (which are objects) and return it back in numerical values also print them.
When i create an object in main method and pass values to my function of return type TwoDPoint,it gives error:- found int,int need TwoDPoiint,TwoDPoint.
// Here is what i tried to do:
Created class TwoDPoint that contains two fields x, y which are of type int. Defined another class TestTwoDPoint, where a main method is defined.In the main method created two TwoDPoint objects.
Then I modified the class TestTwoDPoint and add another function to it. This function takes two TwoDPoints as input and returns the TwoDPoint that is farthest from the point (0,0).
Then I added another function to TestTwoDPoint. This function takes two TwoDPoints as input and returns a new TwoDPoint whose x value is the sum of x values of the input TwoDPoint's and whose y value is the sum of the y values of the input TwoDPoint's.
class TwoDPoint { int x = 2; int y = 4; } class TestTwoDPoint { public static void main(String args[]) { TwoDPoint obj1 = new TwoDPoint(); System.out.println(obj1.x); System.out.println(obj1.y);
I created a superclass Ships and under that a class CivilShips. Under that HumanBulkFreighter.
I declared variables in Ships and CivilShips and wanted to have them set in HBF to a specific value. When I know try to compile them I get the following:
The super keyword when used explicitly in a subclass constructor must be the first statement but what about if i have a this(parameters) statements ? As the this one must also be the first statement... Does this means that i can have only one or the other ? What about when the super constructor is not explicit (aka implicit ) , can i use the this( parameters) in the same constructor ?
Its written that every constructor calls its super class constructor. And we know, constructors are called to create an object. Does it mean that if I am creating an object of a class, I am actually creating objects of all its super class???
I am creating a set of 3 subclasses, 1 superclass, and an application. In my instructions it says to make set methods in my super and subclass by using dialog boxes. In the application you have 3 different arrays where you create objects and are supposed to call the methods from the subclasses to be used in the application. I don't know how to make the dialog boxes from my subclasses to show up in my application.
