1.) Is FileReader class the same as File Class. In my book it uses File class to read data from a file, but one of the members here used FileReader so I was wanting to know if it's identical function or not.
2.) When creating an output file, I will use
PrintWriter outputfile("hello.txt")
i just read a new topic of " appending data to a file," meaning if I want to preserve the old file I would have to use this. From my understanding all this does is prevents the old data from being deleted.
Now, in my code if I type ( "hello.txt",true)this would preserve the old data?
How do you declare methods for a class within the class whilst objects of the class are declared else where?
Say for instance, I have a main class Wall, and another class called Clock, and because they are both GUI based, I want to put a Clock on the Wall, so I have declared an instance object of Clock in the Wall class (Wall extends JFrame, and Clock extends JPanel).
I now want to have methods such as setClock, resetClock in the Clock class, but im having trouble in being able to refer to the Clock object thats been declared in the Wall class.
Is this possible? Or am I trying to do something thats not possible? Or maybe I've missed something really obvious?
I have several different PopupWindows that i want to access from the same fragment. I would like for each PopupWindow to be it's own java file. Here is trimmed down code from an example showPopup.java file,
showPopup.java public class showPopup { //public class showPopup extends Activity implements View.OnClickListener{ //public class showPopup extends Window { public static Context appContext; PopupWindow popupWindow; SQLiteDatabase db; EditText edSpeciesLookup,edSpeciesLookupRowid;
[code]...
How do I configure inheritance to allow showPopup() class to reside in it's own Java file and be called from another class (file)? I've reviewed several hours of online resources as well as my reference books with no productive illumination. I've tried a number of possible implementations and extensions such as "public class showPopup extends Activity implements View.OnClickListener{...", and "public class showPopup extends Window.
Regarding the lifecycle of servlet , in headfirst servlet i can find :
You normally will NOT override the service() method, so the one from HttpServlet will run. The service() method figures out which HTTP method (GET, POST, etc.) is in the request, and invokes the matching doGet() or doPost() method. The doGet() and doPost() inside HttpServlet don’t do anything, so you have to override one or both. This thread dies (or is put back in a Container-managed pool) when service() completes.
How can I call the doGet method of the subclass from the superclass. i am not getting this .
I have a quick polymorphism question. I have a parent class and a sub class that extends the parent class. I then declare an array of parent class but instantiate an index to the sub class using polymorphism. Do I have to have all the same methods in the child class that I do in the parent class? Here is an example of what I mean.
public class ParentClass { public ParentClass(....){ } public String doSomething(){ } } public class ChildClass extends ParentClass { public ChildClass(....)
[Code] ....
Is polymorphism similar to interfaces where the child class needs all the same methods?
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");
i want to write a class in such a way that i should get the current execution time of another class which is running. I searched in net but it shows only how to calculate the time duration of the current class which is running. But as per my way, i need the execution time of one class from another class. How to do this ?
I am working on a program that simulates a bug moving along a horizontal line, My code works correctly when I test it in it's own class but when I tried testing my constructor and methods in a test class I received an error saying, "package stinkBug does not exist" on lines with my methods. However, stinkbug is not a package.
Java Code:
/* * 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. */
How to create object for "class B" and call the "function_B" from other different class D where class D has no connection with class A? Here is my program.
public class A(){ void print(){} } class B{ void function_B(){} } class C{ void function_C(){} }
Here, A, B, C are in the same package. But class D is in different package.
I am a beginner here at JAVA and I am trying to program a Gratuity Calculator using both interface class and object class but it keeps on compiling with errors saying "cannot find symbol".I tried everything to fix it but it just keeps on stating symbol.
[CODE] public class GratuityCalculator extends JFrame { /* declarations */
// color objects Color black = new Color(0, 0, 0); Color white = new Color(255, 255, 255); Color light_gray = new Color(192, 192, 192);
I was doing coding exercise from a book ('OCP Java SE 6 - Practice Exams' by Kathy Sierra and Bert Bates). I came to a question that told to demonstrate the difference between 'default' and 'protected' access rules by creating/making a directory structure and putting a couple of classes in different packages.
For this, I made a total of four classes, out of which, three classes are-Car, TestingCars, CarDimensions. (The fourth is not yet used in testing code till now, so, I am giving only the other three classes.) Their coding is given below.
Out of these classes, the classes- TestingCars and Car - are in a directory (say, FolderName). And, the class- CarDimensions is in FolderName's sub-folder.
The class 'CarDimensions' is public (and its components too are public). And, I am testing all the classes from the class- 'TestingCars'. But, this class (TestingCars) is not able to find the public class- 'CarDimensions' which is in its sub-folder and gives two 'Cannot find symbol' errors citing the class-CarDimensions. Also, If all three classes are put in one single directory, the programs work, without any error.
Coding: Class TestingCars:class TestingCars { public static void main(String[] args) { Car c = new Car(); c.setType("FourWheeler");
[Code]....
I could not find why the public class- CarDimensions- is not getting found by the TestingCars class.
I want to write an app that declares a class Person(String name, int age), and an Account class, Account(int code, double balance).But, additionally, every Person has at most 3 accounts, and each account has a Peron associated with it.
my code so far...
public class Person { private String name; private int age; private Account[] accounts; private int numOfAccounts; public Person(String name,int age){ this.name=name;
[code]....
My problem is:When I make data input for a person, and additionally I want to read data for the account(s) that this rerson has, what code should I write to create a new Account object as account[numOfAccounts].And, what is the code to assign an owner to a new created Account object?
There exists a relationship between the two classes, but I cannot find the way to implement this relation....
public class Sphere { public double diameter; public double volume; public double area; public double fourThirds = 4/3; public Sphere(double someDiameter){ someDiameter = diameter;
[Code] ....
I am trying to get this code so that I only enter the diameter once in the sphere object1 = new Sphere(4); but I can't get it to work right. I can get the diameter to work with the calculate volume and area methods but that's it.
I am working on a project involving a class that has the attributes of one of its inner classes. Now, if possible, I would like to make it so that the inner class is not visible outside of the class. Also, some of the functional mechanics require that the class be an instance of the nested inner class (it extends the inner class). The following code snippet demonstrates the situation.
public class A extends A.B { public static class B { //ideally I would like this to be private/protected. } }
When I try to compile this program, I get the error message "Cyclical inheritance involving A." This error does not make much sense because, since the inner class "B" is static, it requires no instance of "A" (it does not inherit from "A" or uses it). My question is "Is it possible to do something similar to this structure?" I have searched many forums in search of the answer but have not found anything that attempts to explain it. The closest problem that I have found is one relating to the inheritance of a nested inner class from another class. I would like to express that the problem that I am having involves a class defined within the inheriting class.
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);
The assignment is to create a SmartString class that implements a SmartStringInterface class (created by professor) and implements a few methods. We are basically taking a string and then taking various substrings and inserting, deleting them and undoing changes as well. Here are the methods in the interface to use along with the parameters.
public interface SmartStringInterface { public void insert(int pos, String sstring); public void delete(int pos, int count); public void undo(); public String toString();
The Undo is supposed to be able to be called multiple times (to be tested using a driver program that we must create) but the part that's got me is that the changes are only supposed to be stored. Currently, I am storing the "new" string after each change onto a stack, so that undo can just pop off the stack and it will revert to the previous string. Professor said that was wrong, so I don't know how to do it. Here is what I have so far (some of the code we have is using default StackADT stuff from our book, so if you need that I can post as well. You can see in the undo method where I currently save the string. We can use multiple stacks if needed, but the less the better. Must use at least 1. The exception code is already coded for us in another file also. I am only having to code these methods and the driver to test.
import java.util.Arrays; public class ArrayStack<T> implements StackADT<T> private final static int DEFAULT_CAPACITY = 100 private int top; private T[] stack;
i am having a problem while calling a method..i am having a class
Java Code:
public class MySer implements Runnable { public void getMessage(String msg) { ..., }.., } mh_sh_highlight_all('java'); i use the above class in another class
I've a parent class with a argument constructor like below(a sample code)
public class Parent { Parent(String name) { System.out.println(name); } public static void main(String[] args) { } }
Also I've child.class which extends Parent.class as shown below,
public class child extends Parent { child(String name) { super(name); } }
Now, I want create/modify the constructor which is in child, by taking "int i" as an input instead of "String name". How can I do that? Run time I want to execute child constructor not a parent constructor.
Condition is: Without making any changes to the Parent class
