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.

View Replies


ADVERTISEMENT

Cannot Fit Generic Class To Use With Foreach

Oct 7, 2014

I've implemented Stack on the base of the LinkedList. It works as i expect it to work, but then i tried to made it compatible with foreach loop. I've implemented Iterable and Iterator. Code compiles and works fine, but does not return any output. It looks like while working with foreach, next() is not called at all. If i`m getting iterator from instance and try to do iterator.next(), i get output as expected.

public class genericStack<T> implements Iterator<T>, Iterable<T> {
private LinkedList<T> LL ;
protected genericStack() {
this.LL = new LinkedList<T>();
}
public static void main(String[] args) {

[Code] ....

View Replies View Related

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.

View Replies View Related

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.

View Replies View Related

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?

View Replies View Related

Sort 2 Different Objects In Self Made Generic Class Using Comparator

May 31, 2014

Ok here are my 2 Classes

Both have Identical Fields

package com.Lists;
public class EmployeeOffice implements EmpInterface {
private double salary;
private String name;
private String postion;
private double hoursWorked;

[Code] .....

So if i wanna sort this Generic class using comaparator what do i do... I cant find an answer to this... I wanna sort them on the basis of salary what to do ...

View Replies View Related

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?

View Replies View Related

Generic Array Tools

Feb 28, 2014

Trying to make a universal tool for increment an array by one while keeping all the previous values in place.

public K[] increment(K[] k){
int i = 0;
K[] tmp = (K[])new Object[Array.getLength(k)+1];
/*
* Parses through the passed k and fills tmp with all of ks values

[code]...

View Replies View Related

Generic Types In Java

Apr 1, 2014

I am trying to understand the concept of Generics in java. In the introduction to Generic Types, this example is given:

Java Code: public class Box {
private Object object;
public void set(Object object) { this.object = object; }
public Object get() { return object; }
} mh_sh_highlight_all('java'); "Since

Since its methods accept or return an Object, you are free to pass in whatever you want, provided that it is not one of the primitive types." - I understand this.But then it has been changed to a generic class:

Java Code: /**
* Generic version of the Box class.
* @param <T> the type of the value being boxed
*/
public class Box<T> {
// T stands for "Type"
private T t;

public void set(T t) { this.t = t; }
public T get() { return t; }
} mh_sh_highlight_all('java'); "

As you can see, all occurrences of Object are replaced by T. A type variable can be any non-primitive type you specify: any class type, any interface type, any array type, or even another type variable."We can use any type in place of an Object, because Object is a superclass of all classes. But T (or any other class) is not a superclass of all classes. So how do we justify any class being used in place of a random T or any other class?

View Replies View Related

JComboBox Should Be Used In A Generic Manner

Sep 9, 2014

I recently posted that JComboBox should be used in a generic manner. I presumed that once declared, with some type Foo, that one could then do:

Java Code:

JComboxBox<Foo> cb = new JComboBox<>();
// sometime later
Foo foo = cb.getSelectedItem(); mh_sh_highlight_all('java');

However, getSelectedItem() is documented to return a type of Object so a cast is still needed. I can't understand (even for backward compatibility) why it doesn't return a type of the specified type. Many other old classes have been converted to generics so why should this be any different? I just found that one could use getPrototypeDisplayValue() but that seems counter intuitive.

View Replies View Related

JSF :: Using Generic Templates For Managed Beans

Aug 5, 2014

I'm wondering if there's a way to build a template for managed beans which could be extended by a constructor instead of re-writing beans for each entity. I can do that quite easily for Dao objects by creating facades and using those facades to create Dao implementations for specific entities. Not sure if the same concept works for managed beans and haven't really come accross any searches.

I wrote the following but I'm not sure how to implement or even if the concept of generics and templating can be applied to managed beans in the same way it can be applied to Dao classes:

public class BeanTemplate<T> {
private ListDataModel<T> listModel;
@EJB
private GenDao dao;
private Class<T> entityClass;

[Code] .....

The above assumes there's only one method needed in the bean. I thought of extending like this:

public class EmployeeBean extends BeanTemplate<Employee> {
public EmployeeBean() {
super(Employee.class);
}

// how can the methods be called??

Is the same concept for creating dao templates possible for managed beans?

View Replies View Related

Removing (Integer) From A Generic List?

Oct 3, 2014

I am working on a java program that is called OrderedVector which is basically a storage or list that grows and shrinks depending on the amount of data is put in. Most of the methods in my code are correct and working, the only real issue I have lies with either the remove(E obj) method or remove(int index) method. This is the driver I am currently using to test my remove method,

public class Tester {
public static void main(String[] args) {
OrderedListADT<Integer> v;
v = new OrderedVector<Integer>();
for(int i = 0 ; i <= 9; i++){
v.insert(i);

[code]....

the output I am receiving is

Removing 0
Size of data structure is 9
Removing 1
Size of data structure is 8
Removing 2
Size of data structure is 7

[code]....

As you can see, when I am calling the second for loop, none of the elements are being removed by my methods but the first for loop is working just fine.

Here is my code for the OrderedVector

package data_structures;
import java.util.Iterator;
import java.util.NoSuchElementException;
public class OrderedVector<E> implements OrderedListADT<E>{
private int currentSize, maxSize;
private E[] storage;
public OrderedVector(){
currentSize = 0;

[code]....

So overall, my remove method should implement binary search and remove elements using either an index or the object value type.

View Replies View Related

Generic Insertion Sort Program?

Apr 14, 2015

I am working on my generic insertion sort program. When I completed and run my code, I am having trouble with my code. So, I am just trying to see if I get an correct array from a file. However, i just get so many nulls in the array. Therefore, I can't run my insertionSort function because of null values.

Here is my code

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;

[Code].....

View Replies View Related

Generic Instantiation Of A Collection - ArrayList

Nov 18, 2014

So I have a persons class:

public class Person
{
private String name;
private int age;
 public Person (String name, int age) {
this.name = name;
this.age = age;

[Code] .....

And I need to write a simple main method that creates lots of instances of the Person class and adds them to a generic instantiation of a Collection (ArrayList). And I need to make it so I as a programmer can define how many instances to create.

View Replies View Related

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??

View Replies View Related

Creating Generic Version Of Methods

Jul 21, 2014

So I have this class containing all my Enum types, also including methods for fetching Enum types based on their title attribute:

abstract class Enums {
 static private Landmass getLandmass(String name) {
for ( Landmass l : Landmass.values( ) ) {
if(l.title.equals(name)){
return l;

[Code] .....

The second method (getAttribute) is created by copy-paste and I also need to repeat this exercise with several other types of Enums. This seems like a waste of code however.

Instead, I thought I'd create a generic method for fetching any type of Enums. As far as I could follow the tutorial @ Oracle I need a generic class for this. Thus the EnumHelper class:

abstract class EnumHelper<T> {
 private T getEnum(T type, String name) {
for ( type t : type.values( ) ) {
if(t.title.equals(name)){
return t;
}
}
return null;
}
}

This, however, doesn't compute:

horoscopeEnums.java:234: error: cannot find symbol
for ( type t : type.values( ) ) {
^
symbol: class type
location: class EnumHelper<T>
where T is a type-variable:

[Code] ....

2 errors

To be honest I haven't been able to make much sense of the documentation on generics, thus its no surprise I'm stuck.

View Replies View Related

Generic Exception Handler For All Scenarios

Apr 26, 2013

I want to build a generic exception handler which can be reused in any java j2ee applications. I have java application which is communicating with other 3rd party applications like webservices, webmethods , etc from where we are getting an error code which will be used in our java application to do a lookup to get the respective error message from the resource bundle. Please clarify in such case how I can go with a generic exception handler which will be build separately and will be integrated with Java applications to handle the exceptions and errors.

View Replies View Related

Evaluating Infix Expressions Using Generic Stacks

May 12, 2014

I am given the task to create a program that evaluates infix expressions using two generic stacks, one operator stack and one value stack.

This is my GenStack.java file:

import java.util.*;
public class GenStack<T>{//T is the type parameter
private Node top;//top of stack
public class Node {//defines each node of stack
T value;
Node next;

[Code] ....

I'm having trouble with the eval and apply methods. The eval method doesn't appear to pickup ')' characters, like it doesn't even see them.

View Replies View Related

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?

View Replies View Related

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] ....

View Replies View Related

Generic RPG Game - Java Applet When Adding Subroutine

Jul 11, 2014

I am trying to design a generic RPG game. The issue I am having right now is in my Class I have a subroutine (think that is the correct term) that is basically set up to hold a series of Print Statements. I am really just trying to get some Values that are stored within the Applet, have them assigned to their correct variables and then returned in the print statement. Yet, when I run the applet it just pops up the Applet blank and gives me a long list of errors and I really don't understand when they mean.

Here is the code:

The Class

public class CharacterSheet {
final String NL = System.getProperty("line.separator");
public String characterName;
int playerStr;
int playerCha;

[Code] ....

And the error messages:

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException: String is null
at sun.java2d.SunGraphics2D.drawString(Unknown Source)
at TFApplet.paint(TFApplet.java:15)
at javax.swing.RepaintManager$3.run(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)

[Code] .....

View Replies View Related

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"

View Replies View Related

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?

View Replies View Related

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.

View Replies View Related

Array Based Implementation Of A Stack - Generic Array Creation

Oct 10, 2014

So I have this stack. I'm writing out all the operations and what not but I'm having trouble bypassing this "generic array creation" problem. I'm meant to be creating an array based implementation of a stack and from my research from google and my various attempts at things, I have not found a solution that works.

In addition; I have all the operations written that I need except for one final one. And that is clear(). clear() is meant to empty the array, essentially it is a popAll() method. Then all I need to do is set up so I can print out the arrays and I should be able to handle everything else.

StackInterface:

/**
An interface for the ADT stack.
*/
public interface StackInterface<T>
{
/** Adds a new entry to the top of this stack.
@param newEntry an object to be added to the stack */
public void push(T newEntry);

/** Removes and returns this stackÕs top entry.
@return either the object at the top of the stack or, if the stack is empty before the operation, null
*/
public T pop();

[Code] ....

View Replies View Related

Accessing Parent Class Method Using Child Class Object?

Feb 4, 2015

I want to know is there any way we can call parent class method using child class object without using super keyword in class B in the following program like we can do in c++ by using scoop resolution operator

class A{
public void hello(){
System.out.println("hello");
}
}
class B extends A{
public void hello(){
//super.hello();
System.out.println("hello1");

[code]....

View Replies View Related







Copyrights 2005-15 www.BigResource.com, All rights reserved