Can Interface Extend A Class

May 16, 2014

Can 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]....

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How To Implement Interface And Extend Class

Apr 12, 2014

how to 'implement' an interface and 'extend' a class. Now I want to try and recall the information by memory without using any reference material.
Implementing an interface...

Java Code: //This interface will hold information for cell phones//Like saying... you can't BE a cell phone unless you have this information, at the very least

public interface CellInfo {
public void model();
public void make();
public void androidVer();

}

//Now I implement the interface for a class called Galaxy, which is a class about a specific phone

public class Galaxy implements CellInfo
public void model() {
System.out.println("I'm a Galaxy S5.");
}

public void make() {
System.out.println("I'm made by Samsung.");

[code]....

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Stack Overflow Error For Anonymous Class That Extend Interface

Jun 22, 2014

In the following program i have called the anonymous class of dev class.

interface emp {
void desig();
}
public class dev implements emp {
dev e = new dev() //this line is throwing error ...works fine if i use emp instead of dev {

[Code] .....

i am getting stack over flow error as :

Exception in thread "main" java.lang.StackOverflowError
at dev$1.<init>(dev.java:17)
at dev.<init>(dev.java:16)
at dev$1.<init>(dev.java:17)

[Code] .....

Is it because the jvm is not able to decide which of the 2 desigs() it has to load in the memory when its object is created in the main..??

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How To Extend HashCode Method In Class

Nov 3, 2014

I want to extend hashCode method in my class. As we know that hashCode is generating with 32 bit. Now I wanna generate 64-bit hashCode for user given Input.. Input may be string or Integer.

Please let me know.. take me out from this problem..

MY code follows like this...

package hash_table;
public class Hash_table
{
private int num;
private String data;
public boolean equals(Object obj)
{
if(this == obj)

[Code]...

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How To Use JFrame In Child Class - Two Extend Calls

Feb 4, 2014

I am working with a program where I am required to use a JFrame in a child class. The only way that I know how to access a JFrame is to do, example (public class Example extends JFrame), but since it is already extending the parent class, I am kind of stuck. I do not think that you can extend two separate classes, so..... I am stuck.

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Interface Class And Object Class Is Compiling Symbol Errors

Nov 16, 2014

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);
 
[code]....

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When To Use Interface And Abstract Class

Apr 17, 2014

I 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?

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When A Class Or Interface Will Be Initialized

Sep 18, 2014

class Super { static String ID = "QBANK"; }
class Sub extends Super{
static { System.out.print("In Sub"); }
} public class Test{
public static void main(String[] args){
System.out.println(Sub.ID);
}
}

According to me output should be "QBANK" In Sub...BECAUSE sub default constructor will call super() constructor.. below is the definition in jls which i am unable to understand ....

A class or interface type T will be initialized at its first active use, which occurs if:

T is a class and a method actually declared in T (rather than inherited from a superclass) is invoked.

T is a class and a constructor for class T is invoked, or T1 is an array with element type T, and an array of type T1 is created.

A non-constant field declared in T (rather than inherited from a superclass or superinterface) is used or assigned. A constant field is one that is (explicitly or implicitly) both final and static, and that is initialized with the value of a compile-time constant expression . Java specifies that a reference to a constant field must be resolved at compile time to a copy of the compile-time constant value, so uses of such a field are never active uses.

All other uses of a type are passive. A reference to a field is an active use of only the class or interface that actually declares it, even though it might be referred to through the name of a subclass, a subinterface, or a class that implements an interface.

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Anonymous Inner Class For Interface

Jul 29, 2014

I am new to java coding.... When we create anonymous inner class for interface, we get one object for the sublcass of that interface .

In interface there is no constructor then how do we get that object. We know that to create Anonymous inner class we should use one super class constructor.

Whether my understand is correct or not.

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Difference Between Abstract Class And Interface?

May 18, 2011

Difference between Abstract class and Interface??

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Creating Class Inside A Interface

Jun 22, 2014

I am not able to understand how we are able to create an object of static inner class defined inside an interface .

interface outer {
class inner {
void disp() {
System.out.println("inside disp");

[Code] ....

output:

inside disp

How am i able to create a new object for static class?

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Reason To Create Inner Class In Interface

Mar 3, 2012

interface Interface{
class B{
}
}

I know that we can create an inner class inside an interface but i want to know that why we'll create an inner class inside an interface. I mean what is the use of creating inner class inside an interface and what is the advantage of it.

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Can A Class Be Defined Inside Interface

Feb 15, 2014

Can a class be defined inside an Interface .

interface Inter{
class x{
public static void main(String[] args){
System.out.println("Hello World!");
}
}
}

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Can Declare A Class Inside Interface?

May 8, 2013

I have a doubt regarding to java.

Can we declare a class inside an interface?

Ans :yes

But what will be the situation?

I am not getting why it is required...........

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Interface Inside Abstract Class

Jul 8, 2015

What this interface inside that abstract class does. Looking for some examples to how can i use it .... 

public abstract class Expression {
  public abstract String toString();
  public abstract SimpleExpression evaluate();
  public void show() {
  System.out.println(this + " = " + evaluate());

[Code] ....

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List Interface Class That Has Operations For Linked List And LList Class

Oct 6, 2014

I have this ListInterface class that has operations for my linked list and a LList class. The Llist and ListInterface classes are perfect. My job is to create a driver, or a demo class that showcases these operations. That being said, heres the driver so far:

import java.util.*;
public abstract class DriverWilson implements ListInterface
{
public static void main(String[] args)
{

LList a = new LList();

[code]....

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Getting Error - Class Interface Or Enum Expected

Aug 7, 2014

import java.io.*;
class addition {
public static void main(String[] args) {
int num1,num2,sum;
try {
DataInputStream x=new DatainputStream(system.in);

[Code] ,,,,,

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Create And Simulate ATM Interface Using Scanner Class

Sep 28, 2014

I need to create and simulate an ATM interface for my computer programming class using scanner class, if else & switch statements. I've been working on this assignment all day and I'm still no closer to figuring out how to do it. I'm currently working in NetBeans to try and solve it. I have attached the pdf , what I need to do. This is what I have so far:

package bankatmifelse;
//Gator Bank ATM Program
import java.util.Scanner;
public class BankATMIfElse {

[code]...

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Java Interface - Implement Method In Another Class

Sep 17, 2014

So 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?

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Widget Class That Implement Comparable Interface

Mar 15, 2014

Below is the requirements and code. I am getting the error CODELAB ANALYSIS: LOGICAL ERROR(S)We think you might want to consider using: >

Hints:

-Correct solutions that use equals almost certainly also uses high
-Correct solutions that use equals almost certainly also uses low

Assume the existence of a Widget class that implements the Comparable interface and thus has a compareTo method that accepts an Object parameter and returns an int . Write an efficient static method , getWidgetMatch, that has two parameters . The first parameter is a reference to a Widget object . The second parameter is a potentially very large array of Widget objects that has been sorted in ascending order based on the Widget compareTo method . The getWidgetMatch searches for an element in the array that matches the first parameter on the basis of the equals method and returns true if found and false otherwise.

public static boolean getWidgetMatch(Widget a, Widget[] b){
int bot=0;
int top=b.length-1;
int x = 0;
int y=0;
while (bot >= top)

[code]....

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Test To See If Object Is Instance Of Interface Class

Mar 7, 2015

I am currently trying to use Junit to test a whole bunch of stuff. I almost have full line coverage but I am getting hung up on testing an if statement that consists of whether or not an object is an instance of another class. This class happens to be an interface, and even the object is an interface. Weird I know but I just want to know how to get into that if statement. I realize testing interfaces might be a waste of time but I still really want to know how. Here is an example of what I am trying to test:

Java Code:

if(x instance of y){ //where x and y are both interface objects
doSomething();
} mh_sh_highlight_all('java');

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Why Interface Inherit All Non Final Methods From Object Class

Jan 8, 2014

why interfaces inherit prototype of all the non final methods of the object class in itself? Object class is parent class of all the class and Interface is not the class.

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Servlets :: How To Know Which Class Will Implement Which Session Listener Interface

Jan 23, 2015

how it is decided which class will implement a session listener interface? Which class will implement HttpSessionListener? Which one will implement HttpSessionActivationListener, HttpSessionBindingListener or HttpSessionAttributeListener?

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How To Enforce Any Class Which Implements Interface Should Also Implement Comparable Too

Dec 15, 2014

How do you enforce any class which implements an interface should also implement comparable too? Say for instance you may have an interface

public interface Task
{ ... }
public class DoThis implements Task { ... }
public class DoThis1 implements Task { ... }

I want all of the classes which implements the interface Task to implement comparable too. Of course I can just say implements Task, Comparable. But is there something which we could do from interface level, i mean interface Task level?

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Method That Return Instance Of A Class That Implement Iterator Interface

Apr 14, 2015

I have been researching the Iterator and making a class implement iterable. I have seen this example shown below and was wondering how I could change this so that iterable() is not called upon in the main. I would like to be able to make a method that returns an instance of a class that implements the Iterator interface hopefully an inner class. This is because my program will not have a main and will be supplied with a main that includes a new Object with will use the iterator method.

import java.util.*;
public class IteratorDemo {
public static void main(String args[]) {
// Create an array list
ArrayList al = new ArrayList();
// add elements to the array list
al.add("C");

[Code] ....

This is all I have been able to understand from what I want to do. This does not work and this is what I am trying to achieve

public class MyArrayList implements Iterable {
public static final int DEFAULT_SIZE = 5;
public static final int EXPANSION = 5;
private int capacity;
private int size;
private Object[] items;
 
[Code] ...

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What Are Benefits Of Using Interface Plus Abstract Class Over Just Abstract Class

Oct 8, 2014

What are the benefits of using an Interface plus an abstract class, over just an abstract class?

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