Singleton Pattern In Java
Apr 21, 2003I have heard about using patterns in core java.Is it possible?If yes, how?
View Replies
ADVERTISEMENT
Singleton Pattern - Static Field And Public Constructor
Apr 4, 2014In singleton pattern just having a static field is not enough? Do we really need to have a private constructor?
I can have a static field and have a public constructor and still say it is singleton.
Pattern Matches In Java
Jul 3, 2014I have code which validate code enter by user
the requirement say the maxlength=2 and minlength=1 and is a string
the user can enter code as follows
00
A1
HH
12
10
09
I have this Java Code:
public boolean isValidPattern(String s_value, String s_pattern) {
boolean flag = false;
if (Pattern.matches(s_pattern, s_value)) {
flag = true;
}
return flag;
[Code] ....
My problem is when user put
A1 AM geting error
Composition Pattern In Java
Jun 27, 2014I'm having a hard time implementing a simple composition example in Java:
Java Code:
public class CompositionPattern {
public static void main(String[] args) {
Udp udp = new Udp();
Imap imap = new Imap();
udp.startService();
imap.startService();
[Code] ....
The above won't compile. It says "The method supportsMe() is undefined for the type Object". I understand that I stored parent as an Object. But in reality it is not simply Object, but a Udp object or Imap object. The point is to make Responder generic. I don't want to have to cast the Object to Udp or Imap. Any solutions so I can keep this generic?
Recursion Pattern In Java
Jul 16, 2014The program I'm working on is supposed to read input from a file and using recursion, print the pattern of asterisks for each value until the value is either < 0 or > 25. For example, if the value was 4, the pattern would look like this
*
* *
* * *
* * * *
* * *
* *
*
The values are stored in a file entitled prog3.dat which looks like this
4
3
15
26
0
I've never used recursion before and haven't been able to find anything showing how it would work with this particular type of problem. Here is what I've been able to come up with so far, but I'm having problems still which I will show following the code.
import java.util.Scanner;
import java.io.*;
public class Program3 {
public static void main(String[] args) throws Exception {
int num = 0;
java.io.File file = new java.io.File("../instr/prog3.dat");
Scanner fin = new Scanner(file);
[Code] ....
Output:
Please enter an integer
*
* *
* * *
* * * *
Please enter an integer
*
* *
* * *
Please enter an integer
*
* *
* * *
* * * *
* * * * *
* * * * * *
* * * * * * *
* * * * * * * *
* * * * * * * * *
* * * * * * * * * *
* * * * * * * * * * *
* * * * * * * * * * * *
* * * * * * * * * * * * *
* * * * * * * * * * * * * *
* * * * * * * * * * * * * * *
Please enter an integer
Please enter an integer
As you can see, I don't know how to make it print the pattern like in the example and am honestly not even sure if this is recursion since I've never actually worked with recursion before.
Pattern Matches In Java
Jul 3, 2014I have code which validate code enter by user. The requirement say the maxlength=2 and minlength=1 and is a string, the user can enter code as follows :
00
A1
HH
12
10
09
I have this code
public boolean isValidPattern(String s_value, String s_pattern) {
boolean flag = false;
if (Pattern.matches(s_pattern, s_value)) {
flag = true;
[Code] .....
my problem is when i put
A1 is still giving error
Java Program That Prints Specific Numbers In Pattern
Dec 30, 2014Write a java program that prints 0..........121..........23432..........3456543............456787654............56789098765 in this pattern?
My code:
public class Number {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
int k=0;
for(int n=0; n<=10; n=n+2)
[code]....
Java-8 :: Method Reference Does Not Work With Decorator Pattern
Mar 28, 2014I faced with a problem, when I use method reference as a function in Collectors.groupingBy I get an error: "no suitable method found for collect". But! if I replaced method reference with a lambda expression everything works fine.
Here is the code sample:
interface Iface{
public int getPropertyOfClassA();
public void setPropertyOfClassA(int propertyOfClassA);
}
class A implements Iface{
private int propertyOfClassA;
[Code] ....
Change "C::getPropertyOfClassA" with "objC -> objC.getPropertyOfClassA()" and it works!
Write Program For Diamond Shape In JAVA For Given Sample Pattern?
Oct 5, 2014My son want to create a java program (Diamond shape) that can plot graph for with the following data.
Pattern type is:
* *
* *
*
* *
* *
*
How To Use Serialization In Singleton
Nov 28, 2014What is serialization in Java ?how to use serialization in Singleton?
View Replies View RelatedWhat Is The Need For Singleton Class
Jun 12, 2013If i am correct, a singleton class is the one for which only one object is allowed to create right. so why can't i just use everything in that as static and access them using the class name ? what is the need to create a single object ?
View Replies View RelatedTo Obtain Explanation On Singleton Implementation
Jan 11, 2014I've found following code for Singleton Implementation from this forum, I am having a difficulty of understanding following,
1. When Singleton instance will be created, ( From which call ) ?
2. What feature of Static Inner class allow object to be singleton ?
3. How Inner Class implementation is thread safe ?
4. What will happen if variable "instance" mark as non-static, Will it still grantee singleton implementation ?
Java Code:
public class Singleton {
// Note private constructor
private Singleton() {}
private static class SingletonInner {
private final static Singleton instance = new Singleton();
}
public static Singleton getInstance() {
return SingletonInner.instance;
}
} mh_sh_highlight_all('java');
Singleton For DirContext For LDAP Configuration
Aug 9, 2013I want to create a singleton for DirContext for LDAP configuration, hence i have used the initialize on demandclass holder idiom as shown below
public class SlmApplicationContext {
/**
* inner class to hold the instance.
*/
private static class Holder {
private static DirContext instance = new InitialDirContext();
}
/**
* Method to get the singleton instance of this class.
* @return SlmApplicationContext
*/
public static SlmApplicationContext getInstance() {
return Holder.instance; }
...
}
Now the problem is if i close the DirContext.close(), when the next request comes the singleton wont work as the dir context is already closed, hence it will create a new dir context for each requests. Which breaks the singleton concept, hence how we can ensure the singleton works fine even with DirContext.close()?
Implement Singleton - Loading Resource Bundle Only Once For JVM
Jun 20, 2014When I browsed I came to know two ways of implementing singleton.. I dont know which is best.. I am implementing this to load resource bundle only once for my jvm using constructor to getBundle.
public class bundle {
private final static Logger LOGGER = Logger.getLogger(bundle .class.getName());
private static bundle instance;
private static ResourceBundle messages;
private bundle () {
messages = ResourceBundle.getBundle("pb", Locale.getDefault());
[Code] ....
and I am calling this as bundle.getInstance.getMessage("hi");I wanted to knw which option is better and why.. and in the second case how can i call the getMessage() method?
When Close Out Singleton JFrame And Then Open It Again - Components Are Gone
Nov 30, 2014I made UpdateInmateDisplayer a Singleton so that I could access it from the private class ButtonHandler. It works to display the first inmate's number on the screen but when I close out the window and click the Book Inmate button in CurInmatesDisplayer again, it only shows a blank window. I've tried adding the components again from the ButtonHandler in CurInmatesDisplayer but it doesn't work.
View Replies View RelatedUsing Factory And Singleton Design Patterns To Create A Simple Form
Nov 16, 2014My assignment was to create a simple form that demonstrates the use of the factory and singleton design patterns. "Use the Factory pattern to ensure that each form input consists of a text label and a textfield. Use the Singleton pattern for the submit button. When the submit button is clicked, a pop-up should show all the information that was typed into all of the form fields."
I used JFrame to create the form without the design patterns and I although I get the desired result, I'm not quite sure how I can integrate the design patterns into the code I wrote. The example I have to go off uses shapes, not text fields so I think that's why I'm not quite clear on how to approach this.
Here's my code so far:
import javax.swing.event.*;
import javax.swing.*;
import java.awt.*;
[Code]....
Factory And Singleton Design Patterns - Building A Simple Form
Nov 20, 2014My assignment was to create a simple form that demonstrates the use of the factory and singleton design patterns. "Use the Factory pattern to ensure that each form input consists of a text label and a textfield. Use the Singleton pattern for the submit button."
Here's what I have:
Form.java file
interface Form {
public void getFormField ();
}
Name.java file (I have a similar files just like this for Address.java, City.java, State.java, Zip.java and Phone.java)
import java.util.Scanner;
class Name implements Form
[Code] ....
It compiles at the moment but I get a null pointer exception in the main method of the FormFactoryDemo file.
Enterprise JavaBeans :: Calling Singleton Bean From Session Bean Returns NullPointerException
Feb 23, 2013I am doing this
@Startup
@Singleton
@ConcurrencyManagement(ConcurrencyManagementType.CONTAINER)
@Lock(LockType.READ)
public class ResourceBean {
[Code] ....
And I call this singleton bean from a stateless session bean like this
@Stateless
public class ClientBean {
@EJB
ResourceBean resource;
public String create(String r)
{
String res=resource.returnString(r);
return res;
}
}
But resource.returnString(r); gives a org.apache.jasper.JasperException: java.lang.NullPointerException I started the glassfish server in debug mode and found out that "resource" was null. but @PostConstruct in singleton does print which means singleton bean exists.
Can we call singleton beans with no interface in such a way form a session bean? I actually want to acquire instance of singleton bean when a client invokes method in Client bean...
How To Add Spaces To A Pattern
Apr 21, 2015I have created this program that outputs
1
12
123
1234
12345
123456
I tried looking up some ways to create spaces in between each number, but I failed miserably. Here is what I have right now.
public class Iterations {
public static void main(String[] args){
for(int i=1;i<=6;i++)
{
for(int j=1;j<=i;j++)
System.out.print(j);
[Code] ....
Printing Pattern When Name Is Given
Mar 10, 2014I want to know how to print this type of pattern when a name is given ???
Example:
name given TEJA
Capture.PNG
How To Apply Format Pattern
Jan 12, 2015I am able to get Cpu speed using my GetProcessorSpeed method and It returns this output 1796. How can apply this pattern "#.##". I am trying something like this.
Format formatter=new DecimalFormat("#.##");
formatter.format(MainClass.GetProcessorSpeed());
label2.setText(formatter.toString());
Head First Design Pattern
Jan 11, 2014I was reading head first java and the author told to read head first design pattern next.
View Replies View RelatedString Pattern Match
Apr 24, 2015Why the following string fails the test below:
@Pattern(regexp = "^[_a-zA-Z0-9-]+(.[_a-zA-Z0-9-]+)*@[a-zA-Z0-9-]+(.[a-zA-Z0-9-]+)*.(([0-9]{1,3})|" +
"([a-zA-Z]{2,3})|(aero|coop|info|museum|name))$", message = "Not a well-formed email address")
Create A Pattern Of Stars
Jul 2, 2014So I'm studying for a test i have coming up on recursion so i was playing around with it. I ended up making a pattern of stars that look that such :
*
**
***
The code i had for that was
public void makePattern(int size){
if(size == 0){
System.out.println();
}
else if(size > 0){
System.out.print("*");
makePattern(size - 1);
}
}
I was wondering if i wanted to expand on this and make it do something like
*
**
***
**
*
What condition would i have to add i was struggling trying to figure it out...
Inheritance For Word Pattern
Apr 24, 2014I am in an intro programming class and we got assigned a problem for creating a super class with about a dozen sub classes for generating a random word(via WordGetter class) and then comparing that word to a variety of different patterns(like: does the word contain "re"). We were given the super class which looks like this...
public class Pattern {
public boolean matches(String text) {
return true;
}
public String toString() {
return "(TRUE)";
[code]...
and from this class, we have to write subclasses that override those three methods. I am struggling to understand inheritance and I am not really sure where to even start. Here is the instructions for the first sub class we need to write...
"CONTAINS" SUBCLASS
Constructor: The constructor accepts a String named ‘letters’.
Matches: This pattern matches any text that contains at least one occurrence of each ‘letter’.
toString: produces the text “(CONTAINS <LETTERS>)” where <LETTERS> is the ‘letters’ string.
getLetters(): this method must return letters.
equals(Object): careful on this one. Two Contains are equal if they have the same letters (order is not relevant).
(Example):
Pattern p = new Contains(“re”);
boolean f1 = p.matches(“renew”); // f1 is true
boolean f2 = p.matches(“zoo”); // f2 is false
String s = p.toString(); // s is “(CONTAINS re)”
boolean f3 = p.equals(new Contains(“er”)); // f3 is true.. really..
Triangle Pattern (For Loop)
Feb 21, 2015I'm trying to make a triangle which should look like this. But I cant seem o figure it out.
1
2 1
4 2 1
8 4 2 1
16 8 4 2 1
32 16 8 4 2 1
64 32 16 8 4 2 1
128 64 32 16 8 4 2 1
This is the code I have written so far.
public class TestProgram
{
public static void main(String[]args)
{
for (int columns=0; columns<=8; columns++)
{
for (int rows=columns; rows>=1; rows --)
{
System.out.print(rows+ " ");
}
System.out.println();
}
}
}