kevin Abel

// This example shows how to define and use a class in Groovy.

I copied this groovy code from chatgpt.  Jshell gave a bunch of errors.   I don't think it likes groovy.

class Person {    String name    int age    // Method to return a greeting    String greet() {        return "Hello, my name is $name and I am $age years old."    } } // Create a new Person object def person = new Person(name: 'Alice', age: 30) // Call the greet method and print the result println(person.greet())

Jshell is good to know about.  Thank you for introducing me to it.

I'm wondering if it works with groovy.  I'll give it a try someday to find out.

I'm going to go back to working in intelliJ.

I went back to looking at what you recommended that I investigate.  I worked with a tutor who finally got my mind to understand Interfaces.  I didn't use them and I forgot a lot of it after a few months.  I found a folder on my laptop and I think that it has notes from when she was teaching me. I recall an interface being an  class with only one abstract method.   i don't know if that is correct.     I'm going to look at the notes.  

Campbell wrote:Please look at ActionListener and work out why it is a Functional Interface, even though it isn't flagged with that annotation. Hint: you do it by counting methods. Then go to the Java™ Tutorials and find out how I converted the body of the addActionListener() call to a λ expression.

Thanks,

Kevin

Yup.  It worked

After entering the code it said:

modified class SimpleGui3

I added the line to start the code and it ran.

So now how do I use JShell to learn about the code?

I'm enjoying reading the HF book, asking questions, writing/copying code. I'm doing this for fun.  I'd be a good QA white box Java tester.  

Thanks,

Kevin

Campbell Ritchie wrote:Did that code run? It ought to. You simply need to feed SimpleGui3.main(null); to JShell.

:
I'm thinking that I paste the code into JShell.  Then type :

SimpleGui3.main(null);

on the next line and press enter.

I'll see.

Thanks,

Kevin

So far I got the code to run in intellij.

Next I'll use JShell.    

I took a quick look at the links you recommended.   I think the answer to to how many methods there are is "one"  There are methods that all methods automatically have, but these are not counted. Just a guess from what I quickly read.

I have to review lambdas.

I need to chew on this a while.

I already entered the eratta for fixing the page number.  The book didn't say anything about the code not working as presented.  Should I add another eratta and point to this thread?  The material is complicated enough and if the examples don't work it can confuse the reader of the book.  Perhaps the code does work and I pasted the snippets together wrong.  

Thanks,

Kevin

I saw a store that sold party goods yesterday.  I noticed how party is parity without the I.   So here is my joke:

I wonder if the word PARTY comes from the transmitted word PARITY.  Maybe the I bit dropped off and parity was lost.

Perhaps a slogan for a programmer:

We put the IT in parITy.

OK...It's time for me to return to Java.

I pasted your code into Jshell.   I want to get it to run first and then look at how the GUI part works.  

Is there a way to clear memory in Jshell so I can run from the start.  I can't tell if it is remembering objects and variable between runs.

Campbell wrote:Optional. It is possible to call Foo.main(null); on JShell, but that is easier if you declare it as public static void main(String... args). You can then write Foo.main();

Do you mean to use this call to the main method instead of the way shown in your code?

I added two attachments to show what your code looks like in my Jshell editor.

Thanks,

Kevin

I see JShell on my laptop.  I don't remember if I installed it or if it comes with Java.

I read about the tool and watched an introduction video

https://www.theserverside.com/blog/Coffee-Talk-Java-News-Stories-and-Opinions/Java-JShell-Online-Commands-How-to-Tutorial-Exit

The important commands I now know are:

/open

/imports

/exit

The example in the video shows the name of the file with .JSH at the end

/open game.jsh

I'd like to run the code you supplied in JShell.  Do I put your code in a text file and give it a .JSH extension?

Jshell doesn't need the main method.  I don't know if I have to remove it or it is optional.

Thank you,

Kevin

Campbell,

I always appreciate the time and effort you put into answering questions and improving code.  

I learning some main ideas in  the current GUI chapter.  

I didn't write any of the code my self.   I copied it from the book and the repository.  The incorrect page made it difficult to tell what code to use.  

Is the information you gave me needed to make it work or is it for improvements?  

The book mentions to ask questions on Code Ranch which I usually do before posting errata information.  

I have posted at least 16 errata's already.   A lot of the erratas from others don't look as if they were fixed for the May 22 Printing history.

This code example is not working for me.  I wonder if others also got lost.

Do you or someone else communicate with the authors?   Can you give them your input to make this better for the next edition?

I mostly want to learn Java, but I also have a QA mind and don't like to let things go.  I have even challenged the NYC DMV on a written test question.

I'll copy your code into Intellij and get familiar with it.

Thanks,

Kevin

It worked.  Nice sound in the speaker.

Thanks,

Kevin

Campbell,
I have the Third edition
Covers Java 8-17

This thread will make more sense in the GUI area.  

The GUI chapter has been fun to read.  I don't understand it completely.  Maybe once I get the code to work I can look over the code some more.   This is my latest attempt.  It draws an empty window without any objects on it.   I put a break in the method after it uses Random to pick colors.  I hover over the variables that should have values.  Nothing shows on the hover.  Maybe I'm using debug wrong in Intelij.

package guiStuff; import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.util.Random; public class SimpleGui3 implements ActionListener {    private JFrame frame;    public static void main(String[] args) {        SimpleGui3 gui = new SimpleGui3();        gui.go();    }    public void go() {        frame = new JFrame();        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        JButton button = new JButton("Change colors");        button.addActionListener(this);        MyDrawPanel drawPanel = new MyDrawPanel();        frame.setSize(300, 300);        frame.setVisible(true);    }    public void actionPerformed(ActionEvent event) {        frame.repaint();    } } class MyDrawPanel extends JPanel {    public void paintComponent (Graphics g){        Graphics2D g2d = (Graphics2D) g;        Random random = new Random();        int red = random.nextInt(256);        int green = random.nextInt(256);        int blue = random.nextInt(256);        Color startColor = new Color(red,green,blue);       red = random.nextInt(256);       green = random.nextInt(256);       blue = random.nextInt(256);       Color endColor = new Color(red,green,blue);       GradientPaint gradient = new GradientPaint(70,70, startColor, 150, 150, endColor);       g2d.setPaint(gradient);       g2d.fillOval(70,70,100,100);    } }

Carey and Campbell,

I didn't know my comments would be truncated.  Now I"m aware of it.

I'll use the /*           */    comment style          

Thank you,

Kevin

Carey,

I looked more closely at the book.  It shows an outline of the MyDrawPanel Class at the bottom of the page.  It tells the user to go to page 365 for the code but its actually on Page 472.  I added this to the Errata sheet for the book.  

I will add the Class to the code and run it.   I'll review the code to see how it works.

Thanks,

Kevin

I copied the code from the on line examples.  
I don't know what this error means:
MyDrawPanel drawPanel = new MyDrawPanel();  //<-- Cannot resolve symbol 'MyDrawPanel'

This import looks grayed out.  i don't know why
import java.awt.*;

Thanks,
Kevin

package guiStuff; import javax.swing.*; import java.awt.*; import java.awt.event.*; public class SimpleGui3 implements ActionListener {    private JFrame frame;    public static void main(String[] args) {        SimpleGui3 gui = new SimpleGui3();        gui.go();    }    public void go() {        frame = new JFrame();        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        JButton button = new JButton("Change colors");        button.addActionListener(this);        MyDrawPanel drawPanel = new MyDrawPanel();  //<-- Cannot resolve symbol 'MyDrawPanel'        frame.setSize(300, 300);        frame.setVisible(true);    }    public void actionPerformed(ActionEvent event) {        frame.repaint();    } }

I hope it was OK that I I jumped into the discussion.  I hope I didn't hi jack anything.

Thanks,

Kevin