Java-8 :: Method Reference Does Not Work With Decorator Pattern
Mar 28, 2014
I 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!
public class { public static void main(String[] args) { Scanner input = new Scanner(System.in); double[] numbers = new double[10]; System.out.println("Enter " + numbers.length + "numbers"); for (int i = 0; i < numbers.length; i++) { numbers[i] = input.nextDouble();
[Code] .....
I am trying to reference the input "numbers[i]" to my mean method, how do i do that?
If a method is overridden but you use a polymorphic (supertype) reference to refer to the subtype object with the overriding method, the compiler assumes you're calling the supertype version of the method.
is this true? maybe i'm misunderstanding it, but i thought the JVM looks at the object at run time and checks the object type. the context of the quote is about checked exceptions, but it seems like the statement should stand regardless of context. but this doesn't back up my experience. for example:
public class Test{ public void print(){ System.out.println("Super"); } public static void main(String[] args){ Test t = new SubTest();
[Code] ....
Will invoke the subclass method. like i said, maybe i'm missing something.
I am trying to implement the following example to override the equality and hashCode method if the class has reference type member. I do get the expected result "true" for equal and "false" for non-equal objects. But the print statement in the Circle's equal method is not executed when the objects values are not equal. I don't know what i am missing, though i get the equality result "false" as expected for non equal objects.
class Point{ private int x, y; Point (int x, int y) { this.x =x; this.y = y;
So I'm working on a project and noticed that my toString() method won't work. This is just an example of the type of code that I have in my real project. THIS IS MY MAIN CLASS
XML Code:
package trialanderror; import java.util.Scanner; public class TrialAndError { public static void main(String[] args) { Scanner keys = new Scanner(System.in); String name; String phonenumber;
// Display a message, preceded by // the name of the current thread static void threadMessage(String message) { String threadName = Thread.currentThread().getName();
[Code] .....
I want to know How join() and interrupt() method is working on this program?
I have a paint program in Java where I can draw objects. The objects are stored in an arrayList. In the menubar the user can chooce "Back", which means the last item in the arrayList is removed. After that I want the program to loop through the arrayList and draw the remaining items.
My problem is that when I try to do that it will not work from the menu (menuItem2). If I instead add the code to one of the colorpanels (yellowPanel), from where the user can pick colors, it works fine.
menuItem2 uses ActionListener and yellowPanel uses MouseListener. public class PaintProgram extends JFrame implements ActionListener {
This was shown in class the other day and I'm still not sure of how exactly it works, even after looking at it through a debugger.
public void sort(){ for (int i = 0; i < size; i++) { Node temp1 = head; Node temp2 = head; Node temp3 = head; while(temp2.next!=null){ temp3 = temp2.next;
[Code]...
Again, I didn't write this code I'm just trying to understand it. Why specifically do three different temp values need to be used instead of just one like in most sorts?
It is part of a larger program that can be found below.
import java.util.Random; public class MyQueue implements IntegerQueue{ class Node{ Node next; Integer data; Node(Integer data){ this.data = data;
I'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?
The 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
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.
I 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;
I am trying to remove the duplicate elements from ArrayList using .contains() if elements are primitive datatype it works but user-defined datatype does not work.
public class UserBean { String name; String address; public String getName() { return name;
I know in C++ It's possible to pass by reference but what about java?
For example, can i pass the address of a health variable into a Ninja class and then
Since Ninja inherits from an enemy class pass the health into the enemy class and within there have a function that returns that same health address and takes 5 from the health returning 95.
I am unable to understand the meaning of this sentence "final reference variables must be initialized before the constructor completes.",What is trying to imply?
I use this code in Restlet Representation. I try to get the value from the Request API. But I am facing the problem as "Cannot make a static reference to the non-static method getQuery() from the type Resource".
I can't figure out what this error message "Cannot make a static reference to the non-static method getEndUserCharge(long, long, long, long) from the type UpdateUserWS" actually means.
The error is coming from:
public void updateDetailsPackage() { some unrelated code long zero=0; double endUserCharge=0; endUserCharge = UpdateUserWS.getEndUserCharge(long zero, long zero, long zero, long zero); <-------- error is here
I got a project at my university , and we are working with JBoss with the free version WildFly .And also with Java EE.
Now the application is a simple game of Battle Ships or sinking ships to be honest i am not sure as to how the game is actually called.
Registering a user and saving his or her information is not hard using a Stateless java bean , to save the data in the database.
I have a Stateful java bean for every user , the bean is created on the server side after the user succeeds in logging in to the game.
This bean is used mainly for sending an invite from one user to another , to log out the user and everything else that is needed for the user.
The main problem that i encountered here is that JBoss dose not let me have a reference on my frame inside of the bean.
This makes things hard because i would need to use a Timer to ask the bean every second or so if there is an invite from someone , and i would need to save all of the invites .
This was the only thing i could think of .And also implementing the game it self , the communication between users would be complicated more so than i think its needed.
Then my professor said that i could make a service on the clients side in witch i would have a reference of the JFrame , and i could send this service to the java bean and using this service i could get access to the JFrame making things faster.
This would make things a lot easier.For the invite and for the game itself too.
My professor explained that JBoss or WildFly is based on RMI , and he said also that i would need to set up the registry on the server side .But i got lost because i was not sure as to what should i search for .
We are using an older version of WildFly not the newest but one version older , CR1 i think.
And we are also using JPA in the Dynamic web project , server .
I had a TestColor class which contained methods to change hue, saturation, brightness, red, green, blue of TestColor's instances but also had static methods which take in an additional parameter for an instance of TestColor and returns the affected instance of TestColor. Now instead of having one method for every possible color effect to be applied to an image, how can I have one method that takes in an Image parameter, a static or non-static method reference from TestColor parameter and lastly an intensnity value parameter. This is so that I can make an affectedImage object instance inside the method and a Graphics2D object for drawing to each pixel of the new image, now I have one for loop and one nested for loop for the x and y pixels of width and height of the old image and inside the nested for loop I'd create a TestColor by calling getRGB on the image's pixel. Then I would apply the static or non-static method reference somehow to change the color with the intensnity value and after applying it draw to the new Image with Graphics2D. How to would I parametize a method reference and be able to use it in such way?
I use Chrome rather than IE. Recently I got an error message when I tried to deposit a check online.
It said that I needed up get a newer version of Java than 6.10, so I downloaded 7u51.
When I tried to deposit the check again, Chrome asked if I wanted to run the app, and I said yes, but that took me back to the download link again.
I spent almost an hour with my bank experts, but they were unable to solve the problem.
When we tried it on Internet Explorer, it worked fine.
Later, I discovered that on the Java Control Panel under the Default Browser for Java, it has only IE and Mozilla, with the IE being checked and greyed out.
I'm assuming that's why the problems on Chrome, even though up until a few days ago, I was able to deposit checks using Chrome-Java.
