Two first programs: 01 The Basics and 02 Packages

Author: mbarsott

.idea/uiDesigner.xml

@@ -1 +1,17 @@
-# JavaFundamentals
+ # JavaFundamentals
+
+This project intends to quickly show you or remind you the Java syntax and usage for many common constructs and standard Java libraries.
+
+There are explanations as comments inside the code.
+
+Source files are named in a way you can quickly locate the subject you are searching for.
+
+They are also numbered, so they show up in order inside your folder and you can locate them in the Table of contents.
+ 
+ The very first file, JF01_TheBasics, is in the source root (`src`) folder. The others are under 
+ `com/fledger/javafundamentals`.
+
+Table of contents:
+
+1. `JF01_TheBasics`: comments, statements, class, and entry point
+2. `JF02_Packages`: packages and imports

README.md

@@ -0,0 +1,45 @@
+// The Basics - Comments, classes, and entry points
+
+// This is a comment line. Everything after the // is ignored by the Java compiler (until the end of the line).
+
+/*
+    This is a comment block. Everything between "whack asterisk" and "asterisk whack"is ignored...
+    even if it spans multiple lines...
+    or if it is on the line of the comment delimiter. */
+
+/**
+ * This is a Javadoc comment. It is a special type of block comment.
+ * It starts with "whack asterisk asterisk" and is used to generate documentation automatically.
+ * from your Java source code. Javadoc is the name of the tool that generates the documentation.
+ * Read more @ https://en.wikipedia.org/wiki/Javadoc
+ */
+
+// This is a class. Usually classes are written one class per file, on a file with the same name
+// as the class plus the extension ".java".
+public class JF01_TheBasics {
+
+  // This a program entry point. If a method (function of a class) has this exact signature:
+  // public static void main(String[] args)
+  // it can be where your program starts running, the entry point.
+  public static void main(String[] args) {
+
+    // This is a statement and it prints the string "Hello Java Fundamentals" on the console (System.out).
+    System.out.println("Hello Java Fundamentals!");
+
+    // Statements end with a semicolon. Spaces (or tabs, or new line characters) do not matter for the compiler.
+
+  }
+
+  /*
+    To compile and run this program:
+    1. Download and install the Java JDK: http://www.oracle.com/technetwork/java/javase/downloads/index.html
+    recommendation: start out with the latest Java 8 JDK (Java 1.8)
+    2. From the command line, on the directory where this file is, execute the command: javac "JF01_TheBasics.java
+    Obs.: if you list the contents of the folder you should see the file JF01_TheBasics.class (the compiled class)
+    3. From the command line, execute the command "java JF01_TheBasics""
+    Result: you should see the string "Hello Java Fundamentals!" on the screen.
+  */
+}
+
+// Next Source code: JF02_Packages.java
+// This file will be under com/fledger/javafundamentals

src/JF01_TheBasics.java

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+// Packages determine the folder structure of your projects.
+// They are used to organize your source code and create scope to avoid name collisions.
+// If you use a package, it should be the first statement of your  source file.
+// To keep names unique, package names usually start with the domain name inverted
+// ex.: fledger.com -> com.fledger
+// after the domain name you determine the package hierarchy to organize your code
+// The folder structure should reflect the package structure, from the root of source code.
+// ex.: com.fledger.javafundamentals => src/com/fledger/javafundamentals (if src is the root of source code)
+package com.fledger.javafundamentals;
+
+// Imports let you use code from other classes or packages
+
+// The following statement lets you use the class Date from the package java.util:
+import java.util.Date;
+
+// The following statement lets you use any class from the java.text package (including DateFormat):
+import java.text.*;
+
+// The fully qualified name of this class is com.fledger.javafundamentals.JF02_Packages
+public class JF02_Packages {
+
+    // You already know what an entry point is:
+    public static void main(String[] args) {
+      // Creates an object now from the class Date (contains date and time). It is initialized to the current time.
+      Date now = new Date();
+      // Creates an object to format a Date with the long time format.
+      DateFormat dateFormat = DateFormat.getTimeInstance(DateFormat.LONG);
+      // Writes the current time using the long time format.
+      System.out.println("Now it is " + dateFormat.format(now));
+    }
+
+    /*
+      To compile and run this program:
+      1. From the command line, on the source root folder, execute the command:
+      javac com/fledger/javafundamentals/JF02_Packages.java
+      Obs.: it will create JF02_Packages.class in that folder (javafundamentals)
+      2. From the command line, execute the command
+      java com.fledger.javafundamentals.JF02_Packages
+      Notice that you compile (javac) a file (with .java extension)
+      and run (java) a class (with fully qualified name)
+      Result: you should see "Now it is " and the current time, long format, on the screen.
+      By the way, it is about time for you to use an IDE. I recommend Eclipse or IntelliJ Idea Community!
+    */
+}