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Discussion 4 - David Eakes

Discussion 4: Java-to-Smalltalk tutorial

The "Hello, World" program:

public class HelloWorld {

public static void main(String[] args) {
System.out.println("Hello, World.");

or as a Java GUI:

import java.awt.Dimension;
import javax.swing.;
public class HelloWorldGUI {

public static void main(String[] args) {
JFrame frame = new JFrame();
JPanel panel = new JPanel();
panel.setPreferredSize(new Dimension(300, 50));
panel.add(new JLabel("Hello, World."));


t := TextMorph new.
t contents: 'Hello, World.'.
t openInWorld.

In Smalltalk, with morphic, it's very easy to make a call to TextMorph to bring up any text to the main window. In Java, you can get a String to show up in either the console or you have to code up a GUI to display them in. Java code is C-based. Instances have names and must be defined before use. This is not the case in Smalltalk.

Java: Object o = new Object();
Smalltalk: s := Object new.

This look at the syntax brings up an interesting point. In Java, to access an instance, the statement looks connected and enclosed, like the line: panel.setPreferredSize(new Dimension(300, 50));
Everything is enclosed or connected.
Whereas, in Smalltalk, the code is more like a sentence.

These are a few subtle differences, there are many many others. I could list them out, but then you wouldn't learn anything! This is a tips page for going from Java to Smalltalk.

As a final thought, in Java you could look at a source file and edit it based on already existing classes. However, in Smalltalk, you're actually editing the language. That's probably one of the biggest things to remember.

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