Interface Concept In Java
Aug 23, 2014I am having a hard time trying to understand interface concept.
-what is an interface?
-What the use of an interface?
-what does implement or to implement means?
-What does implementation means?
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Concept Of Interface
Aug 22, 2014I am not getting the concept of interfaces.I know they are used to implement multiple inheritances.I also know the example that we create an interface car with certain methods so that a class like bmw which implements the car interface has to implement these methods.But I don't know how interfaces come handy?I don't know the meaning of a class calls a method using an interface?(i know that an interface can not be instantiated).
View Replies View RelatedSending Concept Including Another Concept As Content
Nov 23, 2012I use Jade an I'm able to send messages. Now I try to send a Message with not only integers or strings as content but with another concept as content. Here I want to send a Message of the Media, which contains any number of Trackdata.(I left out the import and other blabla stuff cause i is working)
add(new ConceptSchema(MEDIAINFO), Mediainfo.class);
add(new ConceptSchema(TRACKDATA), Trackdata.class);
//Mediainfo
cs = (ConceptSchema) getSchema(MEDIAINFO);
cs.add(CURRENTTRACK, (PrimitiveSchema) getSchema(BasicOntology.INTEGER), ObjectSchema.MANDATORY);
cs.add(TRACKINFOS, (ConceptSchema) getSchema(TRACKDATA), 1 , ObjectSchema.UNLIMITED);
[code]....
Concept For Innerclass
Apr 3, 2014what does inner class do
View Replies View RelatedUnderstanding Concept Of Static Method
Jun 13, 2014I know that static method cannot use non-static methods .Then how the following code works ,where main method is static and this main method calls go() method which is a non-static method .
import javax.swing.*;
import java.awt.event.*;
public class SimpleGuib implements ActionListener {
JButton button;
public static void main(String[] args) {
SimpleGuib gui = new SimpleGuib() ;
gui.go() ;
[code]....
Grasping Concept Of Throwing Own Exceptions
Dec 3, 2014I am having some difficulties grasping the concept of throwing your own exceptions. How do I get this to repeatedly ask the user to enter a valid value for hours. Also i am having difficulties in the method with using the throw new InvalidHrExcep("That value is invalid"); i cannot get this to work.
public class exceptionProgram {
static Scanner console = new Scanner(System.in);
public static void main(String[] args) throws InvalidHrExcep
{
int day=0;
int month = 0;
int year=0;
int hours=0;
int minutes=0;
int seconds=0;
[code]...
Servlets :: Unable To Understand JSP Session Concept
Mar 10, 2015Any brief introduction about session in java....
View Replies View RelatedWrite A Class Encapsulating Concept Of A Circle?
Mar 19, 2014Prompt: Write a class encapsulating the concept of a circle, assuming a circle has the following attributes: a Point representing the center of the circle, and the radius of the circle, and integer.
Include a constructor, the accessors and mutators, and methods toString and equals.
Also include methods returning the perimeter ( 2 x ๐ x ๐ ) and area ( ๐ x ๐^2) of the circle.
Write a client (application) class to test all the methods in your class. I started out trying to thing how to do this and I mapped out a certain idea but do not know how to incorporate the point represent the center of the circle. I am not sure how to proceed further..
import java.awt.*;
public class Circle {
ย public static void main(String[] args) {
ย
final double PI = 3.14;
int x,y, radius = 4;
double area;
double perimeter;
ย
[Code] ...
Java Interface As Argument
Nov 19, 2014I have 2 files which are as follows:
ICharacterReader.java::
import java.io.EOFException;
public interface ICharacterReader {
char GetNextChar() throws EOFException;
void Dispose();
}
And another file:
SimpleCharacterReader.java::
import java.io.EOFException;
import java.util.Random;
public class SimpleCharacterReader implements ICharacterReader {
private int m_Pos = 0;
[Code] ....
My task is as follows:
1.) Write a class that takes an ICharacterReader interface as an argument and returns a list of word frequencies ordered by word count and then alphabetically.
And also write a main method of a console application that exercises this class using a SimpleCharacterReader, and prints the output to the console.
For example, if the stream returns "It was the best of times, it was the worst of times" then the output will be:
it - 2;
of - 2;
the - 2;
times -2;
was - 2;
best - 1;
worst - 1;
2.) Test the answers in part 1, by writing unit test cases.
How to pass interface as an argument and what is meant by "writing unit test case"?
Interface And Abstract Classes In Java?
Jun 4, 2014why don't I define my methods in a class, rather than going a level up and declaring it first in an abstract class/interface? If the point is to have different implementations for different needs, then we have the option to override the methods.
View Replies View RelatedJava Servlet Interface Is Expected Here
Dec 15, 2014I am absolutely new to Java. I am creating a Servlet and getting the error interface is expected here.
I am using IntelliJ 14.
My Servlet code is as follows:-
package ERPdetector;
import javax.servlet.http.*;
import javax.servlet.*;
import java.io.*;
public class ErpServlet implements HttpServlet {
[Code] ....
Comparing 100 Objects Using Comparator Interface In Java?
Jul 4, 2014Is it possible to compare 100 objects using comparator interface in java?
View Replies View RelatedJava Interface - Implement Method In Another Class
Sep 17, 2014So I created an interface which has the method
int getCalls();
I am trying to implement this method in another class but I'm not sure how to do so. My attempt is:
public getCalls(){ return getCalls(); }
When I run the program it sends the following exception:
Exception in thread "main" java.lang.StackOverflowError
at FibonacciForget.getCalls(FibonacciForget.java:14)
and it highlights the [return getCalls();] part.
What is the correct way to implement the getCalls() method?
How To Do Multiple Inheritance Without Single Interface In Java
Apr 3, 2014how to do multiple inheritance without sing interface in java?
View Replies View RelatedInterface Extends More Than One Interface
Jun 9, 2014Below code gets printed as output?
public interface I1 {
public void method();
}
public interface I2 {
public void method();
}
public interface I3 extends I2, I1 {
[Code] ....
Using Methods Of Interface
Feb 5, 2014I have following code. In this code CSClient is an interface. All methods of CSClient are implementaed in CSClientImpl class. Do I not need CS Client Impl imported in this code ?
How can I call getBranch() of CSClient, which is not implemented in CSClient as " this. getCsClient(). get Branch (new CSVPath(vpath), true);" ? This code works fine without any error in eclipse.
How can a method getBranch(), which is implemented in CSClientImpl class be used in this code without importing CSClientImpl ?
package com.rbc.teamsite.client;
import java.io.File;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
[code]....
Variables In Interface
Jan 21, 2015Variables defined in interface are public static and final so I was thinking that we should not be able to override the variables in a class thats implementing the interface. But when I am compiling the below class, it compiles fine and gives the correct values. but when I did disp.abhi = 35; it gives a compile error (cannot override final variable)
interface display{
int abhi = 10;
void displayName();
[code]....
What Is Marker Interface
Nov 24, 2014what is marker interface?i want to know internal implemenatation and how to write custom marker interface?
View Replies View RelatedInterface As Object?
Aug 6, 2014I'm having trouble understanding the concept of the interface Connection, and PreparedStatement.
1) The simplest way to put it is how is it possible that this code is creating Connection and PreparedStatement objects? I was always under the impression that interfaces cannot be instantiated, but rather implemented. For example I don't see "public class Prepared implements Connection", or "public class Prepared implements PreparedStatement", But I see "Connection con = null;" and "PreparedStatement pst = null;". So it seems as if the interfaces are being used to create objects called con and pst.
2) If in fact these interfaces are being implemented, where are the method blocks in this code that should have been added in order to fulfill the contract?
package zetcode;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
[code]....
Implementing Comparator Interface?
Mar 7, 2014overriding of the compare method.
Here's an example I found:
public class Someone {
String name;
int age;
ArrayList <Someone> listarr = new ArrayList <Someone>();
public Someone(String name1, int age1) {
name = name1;
age = age1;
[code]...
1. In the compare method, what happens when it returns one of the 0, -1, or 1? How does returning such values contribute to the sorting process? How does it take in information (like I know it does through the parameters, but how exactly)?
2. Why do we use the class name for the generics?
Interface Not Updating Properly
Mar 20, 2015The program runs well , it adds the applet but it dosn't update the interface unless I press "_"(Minimize) . To be more clear , the object paints a spring wich goes through 4 stages , it is added to the JFrame but it dosn't uptade until I minimize the frame , that is when it goes to the next stage .
The main class which calls the spring to be added to the frame :
public class principal implements ActionListener ,Runnable{
JTextField field;
JFrame frame;
private class Action implements ActionListener {
public void actionPerformed(ActionEvent event) {
ย frame.repaint();
[Code] .....
When To Use Interface And Abstract Class
Apr 17, 2014I know whats the interfaces and abstract class and also know that difference between interface and abstract class,but here my doubt is eventhough abstract class more advantage than the interface,then why should we use interfaces and when?
View Replies View RelatedInstantiating Interface - ActionListener
Dec 25, 2014I have a snippet here that I'm working with and I have a few questions about it.
button.addActionListener( new ActionListener(){
@Override
public void actionPerformed(ActionEvent ev){
System.out.println("Button Pressed");
}
});
My questions are:
1. How is it possible to use new on ActionListener when ActionListener is an Interface, not a Class. Isn't it illegal to instantiate an Interface?
2. What is going on with the argument to addActionListener? We have the new ActionListener, but we also have a method being defined as well?
Implementing Custom Map Interface
Nov 5, 2014I am supposed to implement a custom Map interface and I'm having some trouble with this method:
// 1. From the interface
/**
* Gives an iterator iterating over the key set from the smallest key that is not less than the key provided.
* @param key the key
* @return the iterator
* @throws NullPointerException if key == null
*/
public Iterator<Key> tailIterator(Key key);
[Code] .....
My implementation is wrong according to a JUnit test. Also, to get a full score this method should have a worst case running time of O(log N), which obviously isn't the case now. (My Map implementation is currently based on binary search in an ordered array, keeping a prallel array for the values).
Can Interface Extend A Class
May 16, 2014Can an interface extend a class?When I am running the following code it's showing some errors..I have commented them.
class A {
public void methodA() {
System.out.println("Class A methodA");
}
}
interface B extends A //interface expected here {
public void methodA();
[code]....
Typecasting Interface To ArrayList?
Dec 16, 2014Can i type cast a interface to ArrayList? suppose there is a interface Named Node.
public interface Node
{
public static final short ELEMENT_NODE=1;
......
.....
}
i want to typecast this interface to ArrayList and fetch all the value.You can use hashtable object class etc.my main moto is to take a value in ArrayList and traverse it.