This is a bit involved, and I want to explain this succinctly without making you read a lot, then show the code. I'm not good at that.
Barebones explanation. In this assignment, we are learning, how to compile,interpret in comand prompt, create a package, create a class and sub-classes, import the sub-classes, and execute println commands in all the sub-classes as a single compiled program, and display such in command prompt. I'm missing something, and the subclass println commands don't display when I run GreetingsClass.java, the Superclass. They are all in the same package. The package directory is com.cisp2030.course, and the three Chapters class files exist in a .Chapters folder inside of .course.
First, GreetingsClass.java:
package com.cisp2030.course;
import com.cisp2030.course.Chapters.*;
public class GreetingsClass
{
Chapter1 c1 = new Chapter1();
Chapter2 c2 = new Chapter2();
Chapter3 c3 = new Chapter3();
public static void main(String[] args)
{
System.out.println("$ Greetings, CISP2030!");
System.out.println(c1);
}
}
This is supposed to import and instantiate the variables of the next code contained as Chapter1.class in .Chapters folder.
package com.cisp2030.course.Chapters;
public class Chapter1
{
public Chapter1()
{
System.out.println("Hello from Chapter1!");
}
}
Just imagine that the above code is one of three that range from Chapter1-Chapter3, and they have been compiled by Command Prompt into class files in their respective directory.
The expected output of compiling, interpreting, and running this program in command prompt should be one program which displays all 3-4 println commands. However, at this time, running hte command prompt only displays the one println command. I think this is because I need to sub-class the Chapter classes to GreetingsClass, and having them imported already, somehow direct GreetingsClass to execute the commands of hte Chapters class files, but I don't know how, and I've googled this consistently, and searched through my textbook and am none the wiser. I think I'm missing something in the code itself, but I don't know enough to come up with any ideas. Any help or advice would be greatly appreciated.
Code has been finished:
package com.cisp2030.course;
import com.cisp2030.course.Chapters.*;
public class GreetingsClass
{
public static void main(String[] args)
{
System.out.println("$ Greetings, CISP2030!");
Chapter1 c1 = new Chapter1();
Chapter2 c2 = new Chapter2();
Chapter3 c3 = new Chapter3();
}
}
Does that even compile?
Java doesn't allow static constructors.
public Chapter1() // removed "static"
{
System.out.println("Hello from Chapter1!");
}
c1 is a member of GreetingsClass. In main() you are in a static method, not a method of GreetingsClass and so you can't access it's members. Most obvious solution is to add GreetingsClass greetings = new GreetingsClass(); to main and try to get c1 out of that.
Related
Ok, so this is what's going on. I'm trying to learn how to use vscode (switching over from jgrasp). I'm trying to run this old school assignment that requires the use of outside .txt files. The .txt files, as well as other classes that I have written are in the same folder and everything. When I try to run this program in JGrasp, it works fine. Though, in VSCode, I get an exception. Not sure what is going wrong here. Thanks Here is an example:
import java.io.*;
public class HangmanMain {
public static final String DICTIONARY_FILE = "dictionary.txt";
public static final boolean SHOW_COUNT = true; // show # of choices left
public static void main(String[] args) throws FileNotFoundException {
System.out.println("Welcome to the cse143 hangman game.");
System.out.println();
// open the dictionary file and read dictionary into an ArrayList
Scanner input = new Scanner(new File(DICTIONARY_FILE));
List<String> dictionary = new ArrayList<String>();
while (input.hasNext()) {
dictionary.add(input.next().toLowerCase());
}
// set basic parameters
Scanner console = new Scanner(System.in);
System.out.print("What length word do you want to use? ");
int length = console.nextInt();
System.out.print("How many wrong answers allowed? ");
int max = console.nextInt();
System.out.println();
//The rest of the program is not shown. This was included just so you guys could see a little bit of it.
If you're not using a project, jGRASP makes the working directory for your program the same one that contains the source file. You are creating the file with a relative path, so it is assumed to be in the working directory. You can print new File(DICTIONARY_FILE).getAbsolutePath() to see where VSCode is looking (probably a separate "classes" directory) and move your data file there, or use an absolute path.
I'm trying to provide completion for positional parameters.
Somewhere I found note that they are not very well supported, but currently I'm not able to find exact place in spec and I'm not sure what that really means.
In meantime I found CompletionCandidatesTest.java in sources which would suggest that they're supported in some fashion or at least prepared to support it.
That's why I would like to know if they work and if yes what I'm doing wrong.
Currently my code in Groovy looks like this:
package com.some.package
import picocli.CommandLine
import picocli.CommandLine.Command
#Command
class TjTest implements Runnable {
static class TjTestCandidates implements Iterable<String> {
#Override
Iterator<String> iterator() {
return Arrays.asList("aaaa", "bbbb", "cccc", "dddd", "eeeee", "ffff").iterator()
}
}
#CommandLine.Option(names = "-x", completionCandidates = TjTestCandidates)
String x;
#CommandLine.Parameters(completionCandidates = TjTestCandidates)
String param;
#Override
public void run() {
println "Start"
println x
println param;
println "Stop"
}
public static void main(String[] args) {
CommandLine.run(new TjTest(), args);
}
}
I performed required bash commands like this:
java -cp "picocli-3.9.5.jar;tj.jar" picocli.AutoComplete -f -n tjtest com.some.package.TjTest
. tjtest_completion
It works like a charm for an option. Unfortunately I was not able to make it work for parameter.
I was also trying to:
remove #Option and leave only #Parameters
put index in parameter
Your code looks fine. The current state (picocli 3.9.5) is that positional parameter completion works in JLine, but not in bash/zsh.
There is an outstanding todo item to fix this. Someone contributed a pull request to address this but it had an issue and has not been merged.
Contributions are welcome!
From all the searching and reading it’s clear that I need to call Platform.runLater() to change the GUI. It also appears I need to use the Runnable interface. Perhaps I should also use Tasks?
But I can’t figure out how exactly I should use them. Plus, I’m not sure which class I should put them in. I’m super new to JavaFX.
My trial JavaFX project has only a Label and a TextField. Label contains a question and the TextField is for answering. Simple enough.
I ran into the problem here:
The answer checking method is in a separate class. I can’t figure out how I can access the components of the GUI/FXML and change them. The methods in the other classes are static while the components of the GUI/FXML are non-static.
Since my actual project would have many quizzes, I'm keen on using separate classes for checking answers.
Only 3 small classes are relevant here:
The “Launcher” class which contains the main method.
The “ViewController” class for the FXML file as well as some methods.
The “Ans” class which has a method to check the answer input.
In which class should I put the Platform.runLater()? And how would the code be?
I’ll just share the code of the “Ans” and the “ViewController” classes.
Ans (The background works are supposed to happen in this file. In the comments, I've mentioned what I want to do but unable to do. For example, I want to set the Label text from there but I can't. Since I have no idea how to do it I've just put a System.out.Println there. In the comments next to it, I've mentioned what I actually want to do.)
package com.dan.ans;
import com.dan.qn.Qn;
import com.dan.view.ViewController;
public class Ans {
public static void checkAns() {
// Checks if the ans is correct.
if (ViewController.getTextFieldInput().equalsIgnoreCase(Qn.getAns())) {
System.out.println("Correct!"); // Here I want the label to say 'Correct!' rather than it be print out in the console.
Qn.setQuestion(); // This gets the next question from the database. But again, I don't know how to make the changes show on the screen. (In the actual code I'd have a separate Label for each of these things)
} else { // Runs if it's not correct.
System.out.println("Incorrect!"); // Here I want the label to say 'Incorrect' rather than it be print out in the console.
}
}
}
ViewController
package com.dan.view;
import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;
import com.dan.ans.Ans;
import com.dan.qn.Qn;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
public class ViewController implements Initializable {
private static String textFieldInput; // I don't know how to access the typed info in the textField from another class. So I store it here and get it from it.
// This is the getter I use for it. (See above)
public static String getTextFieldInput() {
return textFieldInput;
}
#FXML
private Label label;
#FXML
private TextField textField;
#Override
public void initialize(URL location, ResourceBundle resources) {
Qn.setQuestion(); // This method is in the Qn class. It retrieves data from the db file and keeps them in variables.
label.setText(Qn.getQn()); // This sets the label's text using the retrieved data. So you see the first question when the program opens.
}
// Event Listener on TextField[#textField].onAction
public void enter(ActionEvent event) throws IOException {
textFieldInput = textField.getText(); // Stores the typed info in the variable to be accessed from elsewhere.
Ans.checkAns(); // Runs the checkAns to check if the typed answer is correct or not.
}
}
The “Launcher” method just looks like any method with a main class. So I haven’t shared its code here.
Could someone please show me how I can update the components in the GUI from other classes such as “Ans”? I’m pretty sure I should use Platform.runLater() and Runnable. Also may be Tasks. I’ve seen several examples but it’s not clear how I can use it this context.
Thanks a lot in advance! :)
It's not really particularly clear what the issue is here. The natural (to me, anyway) approach would simply be to make the checkAnswer(...) method a method that simply "does what it says on the box", i.e. that takes an answer as a parameter, checks it, and returns a value to the caller indicating if it is correct.
That way you can also avoid all the ugly static hacks.
public class Ans {
public boolean checkAns(String answer) {
// not really sure what Qn is here, but you can also clean this up and
// get rid of the static methods
if (answer.equalsIgnoreCase(Qn.getAns()) {
// not sure if this really belongs here?
Qn.setQuestion(); // really takes no parameters? Sets it to what, then?
return true ;
} else {
return false ;
}
}
}
And then in your controller, you can just do
public class ViewController implements Initializable {
private Ans ans ;
#FXML
private Label label;
#FXML
private TextField textField;
#Override
public void initialize(URL location, ResourceBundle resources) {
ans = new Ans();
// ...
}
// ...
public void enter(ActionEvent event) {
if (ans.checkAns(textField.getText())) {
// update UI to show answer was correct, etc
} else {
// update UI to show answer was incorrect...
}
}
// ...
}
Note how this allows you to maintain proper separation of concerns: the Ans class doesn't need to know anything at all about the UI (which it should not know about at all), and all the UI-specific code is encapsulated in the controller class where it belongs.
It's not really clear why you are asking about Platform.runLater(...) and using Task, since none of the code you posted appears to involve any background threads (i.e. none of this code seems to take an appreciable amount of time to run). If, for example, the checkAns(...) method was doing some remote lookup and did take time to run, you would execute it in a Task and update the UI from the task's onSucceeded handler. See, e.g. Using threads to make database requests. Your question really seems to be more about basic OO design and how to define the relationships between different objects, though; I don't think you are actually asking about threading at all.
Our school project has us make a game using Processing 3. After some studying with the language, our team is pretty confident we can work with the project, though we do have certain reservations of the chosen language.
However, there is one major question we are wondering and could not find an answer. In C++ and many others, when you create a new class in a new file you also create a header file you can include. Does Processing 3 have something similar? I know you can "include" files by adding more tabs, which is still weird but whatever. We would like to have some sort of declarations in advance so we can comment/describe classes and their methods, rather than force each member go through lots of code to find the proper point.
In short, we want to be able to do something like this:
Example.pde
class Example {
//Description
Example();
//Description
void doSomething(int variable);
}
//Other team members don't have to worry past this,
//as they have already seen the public interface
Example::Example()
{
//Constructor
}
void Example::doSomething(int variable)
{
//Function
}
Or do we have to always to like this:
Example.pde
class Example {
//Description
Example()
{
//Constructor
}
//Description
void doSomething(int variable)
{
//Function
}
}
Processing is written in Java, so you can only do things that Java supports. Java does not support header files, so no, you can't use header files in Processing.
However, it sounds like what you're really looking for is an interface.
interface Example {
void doSomething(int variable);
}
class MyExample implements Example{
public MyExample(){
//Constructor
}
void doSomething(int variable){
//Function
}
}
With this, you would only need to show other team members the interface, not the class. As long as they program to the interface, they don't need to ever see the class implementation.
More info on interfaces can be found in the Processing reference.
Trying to do something simple -
I have a set of statements to clear browser cookies:
public void clearCookies () {
selenium.open("http://www.myurl.com");
selenium.waitForPageToLoad("10000");
selenium.deleteAllVisibleCookies();
}
Now, if I use this function in a test script (using TestNG), calls to this work perfectly. However, if I moved this function to a separate class and change the declaration to include "static", the "selenium" keyword is not recognized.
In a configuration class (say configClass),
public static void clearCookies () {
selenium.open("http://www.myurl.com");
selenium.waitForPageToLoad("30000");
selenium.deleteAllVisibleCookies();
}
Now, in my test script, if I call configClass.clearCookies();, I get a runtime error
I tried declaring DefaultSelenium selenium = new DefaultSelenium(null);, in the clearCookies() function, but that too results in a runtime error.
I do have the import com.thoughtworks.selenium.*; import in my configClass.
Any pointers would be appreciated. Thanks.
You can do two things.
Refer to the same selenium object in both the classes i.e. in configClass and the class you are calling configClass.clearCookies().
or else
send selenium object to the clearCookies. So the code would be like this
public static void clearCookies (DefaultSelenium selenium) {
selenium.open("http://www.myurl.com");
selenium.waitForPageToLoad("30000");
selenium.deleteAllVisibleCookies();
}