Interfaces In Java API
May 14, 2014
I understand that interface methods are abstract. I don't understand what the methods in the API do if the method bodies are empty. For example, say there are two interfaces, both with one method with no parameters. What would make these two interfaces different from each other. In the API, the AudioClip interface has the methods play(), stop(), and loop(). If abstract methods have no method bodies, and these methods take no parameters, what makes them different from each other.
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Dec 5, 2014
why interfaces are needed in Java,Now you saw what a class must do to avail itself of the s... - justpaste.it (if I paste the quote here, I get the "Page not found" error after posting -.^)
the first fragment reads that the compiler must be sure that a method exits at a compile time, whereas the second fragment denies it - if a[i] doesn't have the specified compareTo method, a JVM simply throws an exception.
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Jun 16, 2010
Why can't we have static methods in an interface?
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Apr 11, 2014
This is my assignment.
Identify how multiple inheritance is possible in Java with interfaces.
Write a java programme with appropriate classes to demonstrate the above.
Hint: both inheritance and interface concepts are necessary.
For the project name in netbeans, use your id and the name "assignment" separated by underscore,
E.g. 9876543_assignment
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Jan 12, 2014
how can i implement multiple inheritance in java using interfaces. if interfaces have some methods having same name then how to distinguish that ?
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Feb 14, 2014
Interfaces are 100 % abstract classes.They cannot be instantiated.Their sole purpose is to be implemented.So why does the following code works just fine while it is attempting to instantiate an interface.
interface TestA { String toString(); }
public class Test {
public static void main(String[] args) {
System.out.println(new TestA() {
public String toString() { return "test"; }});
}
}
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Sep 1, 2014
Can i use constructors in an interface?
interface AI {
public abstract AI();
public abstract void hello();
}
Output:
I got the error as the method AI() should have return type.
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May 20, 2014
This is the link [URL] and it says One significant difference between classes and interfaces is that classes can have fields whereas interfaces cannot.How can this be possible?
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Jan 8, 2015
In Interview many times Interviewer ask a simple question "Hibernate core Interfaces ?".The five core interfaces exposed by Hibernate. But he not satisfy, Why?...
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Mar 29, 2014
I did research again....
interface:
methods - abstract, default, static ONLY(abstract methods have no body, while static and defaults do, right?)
fields - public, static, final ONLY
abstract class: a normal class, but has at least one abstract method
methods - all
i.e., static, non-static, abstract (can it have a default method?)
fields - all
i.e., public, protected, private / final, non-final / static, non-static
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Jun 20, 2014
When are we allowed to nest interfaces inside a class? Would this be possible? Why or Why not?
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May 8, 2014
I have three classes of object, most of which must implement two out of three interfaces. The interfaces look like this:
public interface Source {
public void startSending();
} public interface Sender {
public void setReceiver();
[Code] .....
That works fine, but I am wondering if pairing the interfaces into subinterfaces is a defensible methodology. For example, all classes that act like Producer must implement both the Source and Sender interfaces. And all classes that act like Relayer must implement the Sender and BlackHole interfaces. I could define two subinterfaces like this:
public interface Factory extends Source, Sender {
}
public interface Modifier extends BlackHole, Sender {
}
I could then define my classes like this:
public class Producer implements Factory {
}
public class Relayer implements Modifier {
}
public class Consumer implements BlackHole {
}
Within the class definitions, it makes no difference, as I will have to implement the same methods either way. But it seems more self-documentary to create the subinterfaces from their parent interfaces and name them in ways that reflect what the classes that implement them must actually do.
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Apr 6, 2014
I am trying to figure out how I can most easily make it easier to make new types of units in my game. I have buildings and ships, and would like to know how I could make it easy to add new units. I have been recently told about interfaces, and have worked with inheritance a little bit.
What I would like to able to do is have it so that all of the variables and methods common to all ships could be stored in a superclass or interface, and same with the buildings. I would also like to be able to assign behaviours to the buildings and ships, maybe as interfaces, which could contain all of the methods and variables required for the functions of that ship or building.
For example, creating a new type of building that can shoot, build ships, and can regenerate nearby ships. So it would possible inherit all of the variables and methods common to all buildings, such as health, image, x, y, getX(), getY() etc. But it would then also gain the variables and methods essential for its functionality, such as shootRange, shoot(), regenRate, etc.
How could this best be achieved?
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Oct 25, 2014
I am reading about interface and i see that classes are allowed inside interfaces which are implicitly static. Here is sample of code i created and i am able to access the static method and fields as well. Here is the code snippet.
public class TestInnerClass {
public static void main(String[] args){
Test.NestedClass.printMe();
}
}
interface Test{
static class NestedClass{
static int x = 100 ;
public static void printMe(){
System.out.println(x);
}
}
}
My question is what is the use of such static classes inside interface? If i don't have access to Foo, i can't ever invoke NestedClass. Whats the design usage?
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Jan 16, 2014
I want to make some library interfaces for a graph.Using these interfaces:
Graph<V,E>
Edge<E>
Vertex<V>
how can i constraint users of this library to use the same type <E> in the graph and edge interface and type <V> in the graph and vertex interface??
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Dec 1, 2014
While reading the design patter book, i got one doubt ,There is a List an interface having sub classes ArrayList, LinkedList etc.,
Q1) My question is Why they declared the List as interface rather than Abstract class?
Q2) i read some site -
List l = new ArrayList(); Why it is GOOD line?
ArrayList l = new ArrayList() ; Why it is BAD line?
Answer required with detailed information for Q1 and Q2.
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Oct 15, 2014
import java.util.*;
public class CommonElements
{
private int comparisons; // number of comparisons made
private Comparable[] arrayToSearch; // current array being traversed
private Comparable[] commonElements = new Comparable[10];
private int arrayPosition = 0; //keeps track of what index to add an element to common at
[Code] ...
I have trying to get this down to the bar minimum. I am trying to cast the desired object array to a array of comparable. This is all required by the assignment.
I am getting a runtime error that I can not perform the desired cast. What do I need to provide the compiler in order to allow for this casting. I can not change the signature of the method however nothing about the class has been specified do I need to implement comparable? Also I don not now what the client is passing so how would I write a generic compareTo method to compare object of unknown types.
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Oct 14, 2014
imagine you are implementing 2 interfaces having identical method signatures:
interface A {
void doStuff();
}
interface B {
void doStuff();
[Code] ....
How can I implement both methods?
Or another example with member variables:
interface A {
public static final int i = 3;
}
interface B {
public static final int i = 33;
[Code] ....
How can I go about making clear which 'i' is meant?
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Sep 12, 2014
I have tried running the java application without adding the site to site list in java security tab. But I get a sand box message as APPLICATION BLOCKED BY SECURITY SETTINGS. How to run the java application without adding the site to site list in java security tab.
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Oct 24, 2014
I want to develop a Java program that uses OpenScript APIs to test my applications. The OpenScript framework automatically creates the Java Code so I was thinking of either using this code or create my own using the APIs.
I tried both options using NetBeans but I'm getting errors everywhere starting with the library import. I'm pretty new to Java so I'm sure I'm missing a lot of things here. I pasted the code below from the OpenScript framework that want to use in a stand-alone file for your reference.,
import oracle.oats.scripting.modules.basic.api.*;
import oracle.oats.scripting.modules.browser.api.*;
import oracle.oats.scripting.modules.functionalTest.api.*;
import oracle.oats.scripting.modules.utilities.api.*;
import oracle.oats.scripting.modules.utilities.api.sql.*;
[Code] ....
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Apr 9, 2015
I've written a java application with several classes all in the same .java file. It works just fine. Now, I've broken it up so that each class has its own .java file. Still works fine. My next step is to put those classes into a package, but I'm not about to get the program to run.The .java source files are all in /home/user/src
I've set the CLASSPATH to /home/user/src..All of the source files have "package com.myfirm.program" on the first line.I compiled the application with:
javac -d . File1.java File2.java File3.java (etc...)
the compiler created the directory: /home/user/src/com/myfirm/program and put all of the .class files in there.So how do I get the program to run? if I run from /home/usr/src
java File1
I get: Exception in thread "main" java.lang.NoClassDefFoundError: File1 (wrong name: com/myfirm/program/Program)
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Apr 14, 2015
I create 2 files:
CircleCalculationMethod.javaMain.java
In Main.java, How can i call method in CircleCalculationMethod.java ?
Should I put everything in same folder ??Should i do something like "import CircleCalculationMethod.java"Should i do something like create a package ...
I use Eclipse software
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Sep 19, 2014
The title of Question might seem old and previously asked.But I have a Question that what is difference between javaSE and Java EE.Although I knew what comes under JavaSE and What is under JavaEE.But My question is that.
What happens when we add PATH in our Environment Variable How does Eclipse or Other IDE use it?
Second Question is.
For Java SE we declare a Path Variable but for Java EE we do not add any library?(I know we add some jar file like for Servlet(Servlet-api.jar) and for EJB(Ejb.jar),But What is actaul difference?
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Oct 23, 2014
creating a program that will output something like this:
Enter an Integer: 1405302(user inputted)
Your integer contains 2 even digit(s), 3 odd digit(s), and 2 zero(s).
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Dec 4, 2014
I know about coding in general, Java, C, Python, SQL etc. but I barely know anything about making code come together on the web. I have a vague idea about what things like libraries and frameworks are,I'm interested in making a web application with which relies on Java do to the data processing. The idea is that the user inputs some messages, clicks submit, the text is taken away and processed, and the results are displayed on the screen. I would like the UI to be smooth with a modern look and feel.
Also, I usually do programming on Windows but I could also use Linux, so if I'll come across any specific drawbacks using Windows.
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Jan 9, 2015
How do I specify the Working directory where the Java app is located? It may be different on different machines.
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