Nesting Interfaces Inside Classes
Jun 20, 2014When are we allowed to nest interfaces inside a class? Would this be possible? Why or Why not?
View Replies
ADVERTISEMENT
Abstract Classes And Interfaces
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
Classes Of Object - Implement Two Out Of Three Interfaces
May 8, 2014I 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.
How To Simplify Classes By Using Interfaces And / Or Inheritance
Apr 6, 2014I 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?
Why Static Classes Are Allowed In Interfaces
Oct 25, 2014I 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?
Why Super Classes Always Declared As Interfaces And Not Abstract Class
Dec 1, 2014While 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.
Java Command - Find All Classes Inside A Package
Aug 21, 2014Is there any command to find all the classes inside a package?
E.g. : To find all the properties and methods inside a class String we use "javap java.lang.String" ....
Nesting Loops - Odd / Even And Zero Digits In Integer Value
Oct 13, 2014So I am trying to do this program but I can't figure out how to nest it properly. The prompt is :
Design and Implement an application that determines and prints the number of odd,even,and zero digits in an integer value read from the keyboard.
The catch is, strings are not allowed. This is what I have so far :
import java.util.Scanner;
public class OddEvenZero {
public static void main(String[] args) {
int zero = 0, even = 0, odd = 0, num, num2;
[Code] ....
How To Draw Multiple Graphics Inside One JPanel Using Multiple Classes
May 5, 2015I'm very new to Java, and I am creating a program that takes multiple user input to create one face. I have a class for the eyes, nose, lips, and headshape. For some reason, my program is not drawing the graphics. ***for question purposes, I have only included my head shape class and my test class****
my "test" class:
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class FaceTest
{
public static void main(String[] args)
{
String head = JOptionPane.showInputDialog("Would you like a circle, square, rectangle shaped head?: ");
[Code] ....
Can Interfaces Be Instantiated
Feb 14, 2014Interfaces 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"; }});
}
}
Using Constructors In Interfaces?
Sep 1, 2014Can 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.
Interfaces In Java API
May 14, 2014I 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.
View Replies View RelatedJavaDocs Says Interfaces Cannot Have Fields?
May 20, 2014This 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?
View Replies View RelatedWhy Interfaces Are Needed In Java
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.
Hibernate Core Interfaces
Jan 8, 2015In Interview many times Interviewer ask a simple question "Hibernate core Interfaces ?".The five core interfaces exposed by Hibernate. But he not satisfy, Why?...
View Replies View RelatedStatic Methods In Java Interfaces?
Jun 16, 2010Why can't we have static methods in an interface?
View Replies View RelatedInterfaces Using Generic Type Constructions
Jan 16, 2014I 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??
How Multiple Inheritance Is Possible In Java With Interfaces
Apr 11, 2014This 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
Implement Multiple Inheritance In Java Using Interfaces?
Jan 12, 2014how can i implement multiple inheritance in java using interfaces. if interfaces have some methods having same name then how to distinguish that ?
View Replies View RelatedCasting And Interfaces - Comparing Object Of Unknown Types
Oct 15, 2014import 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.
Ambiguity When Implementing Multiple Interfaces With Same Method / Variable Names?
Oct 14, 2014imagine 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?
How To Call Classes Within Other Classes
Apr 18, 2014How do you call classes within other classes? Or can you only call classes through the main?
View Replies View RelatedPassing Values To Two Classes And Retrieving Values From Those Classes
Feb 14, 2015I'm doing an aggregation exercise that's suppose to find the volume and surface area of a cylinder. What I'm trying to do is pass values from one class, to a second class, and that second class passes values to a third class.
This may be a clearer explanation: The first class is the main program which sends values to the second and third class. The second class is used do calculations for a circle (a pre-existing class from another assignment). The third class grabs the values that the second class calculated and calculates those values with the one that was passed from the first class to the third class. The first class then prints the outcome.
Problem is when the program gets to the third class, it just calculates the value from the first class with the default constructor from the second class. It's like the second class never received the values from the first class. I think I'm missing a step, but I don't what it is.
First Class:
package circle;
import java.util.Scanner;
public class CylinderInput
{
static Scanner in = new Scanner(System.in);
public static void main(String[] args)
{
//user defined variable
[Code]...
Can For Loop Be Nested Inside If?
Mar 6, 2015Here's what "Why doesn't this work?" question. It concerns a small method which is part of a card game.
I'm trying to check a condition from a section of an array, without a predetermined number of times any given call to this method will require a check. How much of the array I'm checking could vary greatly.
Is it at all possible to nest a for loop yielding a variable number of boolean && conditions inside an if? Am I just missing the right bracketing or is this nesting (if that's the word) even possible in the language?
To clarify, below is broken code. Compiler isn't letting me accomplish this goal as I envision it.
public boolean isFlanking() {
boolean f;
int reach = Math.abs(selectorX - targetX);
if(rival.getDeck()[selectorX].getPile().isEmpty() == true &&
[Code] ....
Switch Inside A Do While Loop?
Oct 10, 2014Basically the problem is I've been trying to loop my switch (if this is even possible) until the user enters a correct number between 1 and 4. But for some reason when the user enters a correct number (1,2,3,4) the loop runs again. Even when the user enters a wrong number the switch ignores the default and repeats what is in the do.
Am I just trying to loop something that cannot be looped or have I gone?
import java.util.Scanner;
class mammals {
int age;
int death;
String name;
[Code].....
Replace Unless Inside Quotes?
Aug 24, 2014Basically, I am trying to write a method that will take a string, a target, and a replacement (a replacement function like string.replace). I want it to replace all instances of target with replacement EXCEPT for instances that occur within single or double quotes.
Example input / output:
this "Wont" be " replaced, be"
call: replace(theString, "replaced", "narf") and replace(theString, "be", "rafn")
output:
this "Wont" rafn " replaced, be"