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HelloWorldSWT tutorial program does not compile [message #1830863]

Wed, 05 August 2020 07:58

Eclipse User

Dear forum members,

I have just installed Eclipse again and tried to follow the HelloWorld tutorial. It worked and I think it also did last time.

Then on to the HelloWorldSWT tutorial, which didn't work last time.

I managed I think to import what the tutorial refers to as the 'SWT project' : On the left of the Eclipse window there is now something called 'org.eclipse.swt'.

I was able to follow the remainder of the tutorial without problem and as the tutorial admits, doing so results in several compilation errors. As a consequence, the program can't run.
The program is as follows :

import jdk.nashorn.tools.Shell;
public class HelloWorldSwT {

	public static void main(String[] args) {
		Display display = new Display() ;
		Shell shell = new Shell(display) ;
		Shell.setText("Hello World !") ;
		shell.open() :
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) display.sleep() ;
		}
		display.dispose() ;
	}
}

Here are the compiler complaints :

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
Display cannot be resolved to a type
Display cannot be resolved to a type
The method setText(String) is undefined for the type Shell
The method open() is undefined for the type Shell
Syntax error on token ":", ; expected
The method isDisposed() is undefined for the type Shell

at HelloWorldSwT.main(HelloWorldSwT.java:6)

I suspect that if I continue using Eclipse, I will encounter that type of problem again. Is there somewhere a good guide explaining how to make Eclipse find stuff ?

Re: HelloWorldSWT tutorial program does not compile [message #1830864 is a reply to message #1830863]

Wed, 05 August 2020 08:06

Eclipse User

Which HelloWorldSWT tutorial?

Re: HelloWorldSWT tutorial program does not compile [message #1830866 is a reply to message #1830864]

Wed, 05 August 2020 09:13

Eclipse User

Sorry that I forgot to mention that. I am talking about the one that is included in Eclipse, called 'Create a Hello World SwT application'.

Re: HelloWorldSWT tutorial program does not compile [message #1831057 is a reply to message #1830866]

Mon, 10 August 2020 20:47

Eclipse User

import jdk.nashorn.tools.Shell; should be import org.eclipse.swt.widgets.Shell;

Re: HelloWorldSWT tutorial program does not compile [message #1831221 is a reply to message #1830863]

Fri, 14 August 2020 03:21

Eclipse User

Thanks.
I made that modification and also corrected the erroneous line 8. The program is now the following :

import org.eclipse.swt.widgets.Shell ;
public class HelloWorldSwT {

	public static void main(String[] args) {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setText("Hello World !") ;
		shell.open() ;
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) display.sleep() ;
		}
		display.dispose() ;
	}
}

When run, the compiler makes these complaints :

Exception in thread "main" java.lang.Error: Unresolved compilation problems:
Display cannot be resolved to a type
Display cannot be resolved to a type
Shell cannot be resolved to a type
Shell cannot be resolved to a type

at HelloWorldSwT.main(HelloWorldSwT.java:7)

Re: HelloWorldSWT tutorial program does not compile [message #1831237 is a reply to message #1831221]

Fri, 14 August 2020 12:48

Eclipse User

See https://git.eclipse.org/c/platform/eclipse.platform.swt.git/tree/examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet1.java. You'll also need to create a dependency on swt.jar such as through placing the jar in a lib folder and adding it to the classpath.

That said, I can't get swt dependency to work on anything later than java 1.8 because it's not modular.

Re: HelloWorldSWT tutorial program does not compile [message #1831304 is a reply to message #1831237]

Mon, 17 August 2020 03:14

Eclipse User

I have added
package org.eclipse.swt.snippets ;
but don't know how to "create a dependency on swt.jar such as through placing the jar in a lib folder and adding it to the classpath. "

It is still not working and I still don't know how to make Eclipse find the stuff it needs.

I did manage to explain Eclipse how to find org.eclipse.swt.widgets.Shell by adding swt.jar to HelloworldSwT.java's build path.

I did some more meddling and now the program compiles.

import org.eclipse.swt.widgets.* ;

public class HelloWorldSwT {

	public static void main(String[] args) {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setText("Hello World !") ;
		shell.open() ;
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) display.sleep() ;
		}
		display.dispose() ;
	}}

I still don't know how to make Eclipse find stuff in general.

I can understand the developpers don't have time to maintain their tutorials, but I can't understand why they don't just delete the faulty ones.

Re: HelloWorldSWT tutorial program does not compile [message #1831458 is a reply to message #1831304]

Thu, 20 August 2020 05:00

Eclipse User

I have written another tiny program where I use UCSDUnfoldingMaps.
However, Eclipse is unable to resolved that to a type.

However, I have that package in the package explorer and for classes inside that package Eclipse can find that class, but outside of it not apparently. On the website unfoldingmaps.org/javadoc/ I don't see explained what Eclipse should be looking for.

Again, how can one make Eclipse find the stuff it needs to run a program ?

Re: HelloWorldSWT tutorial program does not compile [message #1831462 is a reply to message #1831458]

Thu, 20 August 2020 05:58

Eclipse User

I'm confused. I looked over their website and downloaded the "eclipse" package and imported it into eclipse. All their examples seem to use processing.core.PApplet which uses sun.applet.AppletViewer. This hasn't existed since Java 1.8. Their API (javadocs) however are at the level de.fhpotsdam.unfolding.UnfoldingMap which, takes the PApplet as a constructor argument. What are these people doing? Is the library confined to Java 1.8?

Re: HelloWorldSWT tutorial program does not compile [message #1831478 is a reply to message #1831462]

Thu, 20 August 2020 09:08

Eclipse User

It is a package developped by the University of California San Diego. I am sort of following the course Object Oriented programming in Java on Coursera by their computer science department. UCSDUnfoldingMaps is outdated as it relies on the deprecated Papplet (and perhaps for other reasons as well). I finally managed to make it work by (by among other things) using Java 1.8.

Re: HelloWorldSWT tutorial program does not compile [message #1832316 is a reply to message #1830863]

Wed, 16 September 2020 04:17

Eclipse User

Is there really no one who knows how to make Eclipse find stuff ?

I tried importing stuff in the program at the original location again and that worked. Then copied all the code to the file at the original location. Still no red xes. What has changed ? Now there is a folder UCSDUnfoldingMaps in a folder called 'Referenced Libraries', which I suspect wasn't there before.

index.php/fa/38908/0/

Will it run then ? No. When I tell Eclipse to run that program, it gives the error message box : "src/lifeExpectancyPerCountry [in Trials] does not exist", which is rubbish.

How can one show an image without uploading it to a website first ?
Edit : the preview failed to show the image.

Attachment: LifeExpectancy.java in Trials.png
(Size: 13.91KB, Downloaded 796 times)

[Updated on: Wed, 16 September 2020 04:18] by Moderator

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