Interfaces Using Generic Type Constructions

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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Addition Of Generic Type Parameter Causes Member Type Clash

Apr 22, 2014

Got a problem with generics, which I'm still pretty new at. Here's a program that compiles fine:

import java.util.ArrayList;
import javax.swing.JComponent;
public class Experiments {
public static void main(String[] args) {
ListHolder holder = new ListHolder();

[Code] ....

It's useless, but it compiles. If I change Line 14, however, to add a generic type parameter to the ListHolder class, Line 10 no longer compiles:

import java.util.ArrayList;
import javax.swing.JComponent;
public class Experiments {
public static void main(String[] args) {
ListHolder holder = new ListHolder();

[Code] ....

I get this error:

Uncompilable source code - incompatible types: java.lang.Object cannot be converted to javax.swing.JComponent
at experiments.Experiments.main(Experiments.java:10)

Apparently, the introduction of the type parameter leaves the compiler thinking that aList is of type Object. I can cast it, like this:

JComponent c = ((ArrayList<JComponent>)holder.aList).iterator().next();

That makes the compiler happy, but why is it necessary? How does adding the (unused) type parameter to the ListHolder class end up making the compiler think the aList member of an instance of ListHolder is of type Object?

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How To Convert String Type To Generic Class Type

Mar 22, 2015

I have a String repersentaion of some Object.I want that object convert back into some class type how can I do this?

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Type Inference With Constructor Of Generic Class

Jul 15, 2014

I am following this article : [URL] ....

It is important to note that the inference algorithm uses only invocation arguments, target types, and possibly an obvious expected return type to infer types. The inference algorithm does not use results from later in the program.

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Generic Methods Introduce Their Own Type Parameters

Apr 10, 2014

Generic methods are methods that introduce their own type parameters. This is similar to declaring a generic type, but the type parameter's scope is limited to the method where it is declared. Static and non-static generic methods are allowed, as well as generic class constructors.

1. The method is only exclusively to be used for the declared argument parameter? For example given a generic method:public static <String, Integer> boolean method(Pair<K, V> p1) {}I could only invoke the method if Pair argument parameter is <String, Integer>?

2. Or, it will return a <String, Integer> value?

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Type Class Is Not Generic - It Cannot Be Parameterized With Arguments

May 16, 2008

I have set up a project in Eclipse 3.1 and am using java 5.0 compiler.

Here's my folder structure in Eclipse

Java Code:

DFSRemoteClientTestClient.java mh_sh_highlight_all('java');
DFS is the project in Eclipse

And this is how it looks my java class

Java Code:

package RemoteClient;
import java.util.*;
// other imports
public class TestClient {
public static void main(String [] args) throws ServiceInvocationException {
// business logic here ....
}
} mh_sh_highlight_all('java');

So, basically, my java class is just a simple class with a main function.

Now when I build my project, using Project->Clean...

Then I get this as an error at the very first line where i specify the package

This is the error:

Java Code: The type Class is not generic; it cannot be parameterized with arguments <T> mh_sh_highlight_all('java');

What's this error and why am I getting this.

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Adding Any Type Of Data To A Generic List?

Aug 28, 2014

Is this the proper way to add to a generic list? My code works just fine, but I got this feeling that there might be some kind of flaw in it or something. Is this pretty much the basic way to add any type of data to a generic list?

import java.util.LinkedList;
public class ListOfGeneric<E> {
private LinkedList<E> myList;

ListOfGeneric(){
myList = new LinkedList<E>();

[Code] ....

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Generic Method And Bound Type Parameter Errors

Jul 14, 2014

I am following this article [URL] .... till now I have made some code

This is my Interface

public interface Comparable<T> {
public int compareTo(T o);
}

And this is my class where I am using Bound Type Parameter on Generic Methods

public class GenericMethodBoundType {
public static <T extends Comparable<T>> int countGreaterThan(T[] anArray, T elem) {
int count = 0;
for (T e : anArray)

[Code] .....

What else I need to do both in main method and at what parameterized types I need to pass at the class?

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Cannot Assign Generic Object Reference To Similar Type

Jul 26, 2014

I have the following code:

public class CollisionManager<T> {
private boolean collision = false;
private T mainEntity;
public <T extends Entities> void handleCollision(T mainEntity, T secondEntity){
this.mainEntity = mainEntity; // This is illegal.
}
}

Why "this.mainEntity = mainEntity" is incorrect and also show me the correct way to achieve this?

The error I am getting is "Type mismatch: cannot convert T to T"

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Cannot Assign Cloned String Array To Generic Type Array

Jun 21, 2014

I have the following code in which I am looping through the rows of one array (composed of Strings) and copying it to another array. I am using .clone() to achieve this and it seems work as it changes the memory location of the rows themselves. I did notice that the String objects are still pointing to the same location in memory in both arrays but I won't worry about that for now, at the moment I just want to understand why the array I am cloning is not successfully assigning to the other array.

This is the incorrect line: ar[r] = maze[r].clone();

My code:

private String[][] maze = {{"*","*","*"," ","*","*","*","*","*","*"},
{"*"," ", "*"," "," "," ","*"," ","*","*"},
{"*"," ","*","*","*"," ","*"," ","*","*"},
{"*"," "," "," "," "," "," "," "," ","*"},
{"*","*","*","*","*"," ","*","*","*","*"},
{"*","*","*","*","*"," ","*","*","*","*"}};
//private String[][] mazeCopy = copyMaze(new String[6][10]);
private <T> T[][] copyMaze(T[][] ar){
for (int r = 0; r < ar.length; r++){
ar[r] = maze[r].clone();
}
return ar;
}

My compiler says: Required: T[]. Found: java.lang.String[]

Since ar[r] is an array and .clone() also returns an array why is this line incorrect.

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Generic Method In Generic Class

Jul 23, 2014

1 import java.util.ArrayList;
2 import java.util.List;
3
4 public class MyList<E> {
5
6 public List<E> list;
7 public int length;

[code]...

I am trying to define a class MyList, which i just a wrapper around an ArrayList, no real purpose, just for the sake of learning Generics. Idea here is that I create a parameterized class, MyList<E>, which holds a parameterized instance var of type List<E>. I have an add method which adds an element of type E to the List<E>. If I create an instance of MyList, call it 'm', for some reason when I try to call a method on that instance the compiler complains that 'm' cannot be found.

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Can Interfaces Be Instantiated

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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Using Constructors In Interfaces?

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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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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JavaDocs Says Interfaces Cannot Have Fields?

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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Why 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.

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Hibernate Core Interfaces

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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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

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Nesting Interfaces Inside Classes

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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Static Methods In Java Interfaces?

Jun 16, 2010

Why can't we have static methods in an interface?

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Classes Of Object - Implement Two Out Of Three Interfaces

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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How To Simplify Classes By Using Interfaces And / Or Inheritance

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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Why Static Classes Are Allowed In Interfaces

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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How Multiple Inheritance Is Possible In Java With Interfaces

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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Implement Multiple Inheritance In Java Using Interfaces?

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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Getting Int Type Cast To Lower Precision Char Type In Parasoft JTEST

Mar 11, 2014

Below code I am using to typecast int to char.

char escapeValue = (char)0;
char cha = (char) 10;
escapeValue = (char)(escapeValue * cha); // Here am getting the above error.

I have 38 similar issues in my workspace.

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