quick learn java

Hour I. Hello Program, Orientation, and Input
Example I.
class Hello {
  public static void main (String[] args) {
    System.out.println("Welcome to the world of Java Programming.");
  } // method main
} // class Hello
To compile and run this program, you need to have installed JDK and added a line to your path statement referring to the directory of where it was install + \bin. (e.g. path %path%;c:\jdk\bin;)
•    type this file into notepad or something
•    save it as Hello.java(class name + .java)
•    drop to a command prompt
•    type javac Hello.java (e.g. "javac C:\work\Hello.java")
•    type java Hello (e.g. "java C:\work\Hello")
•    then watch the magic
You have now written and completed your first Java program. Looking back to the above program, you should notice the following. First, Java is case-sensitive. The commands have to be written like they are above. Java also denotes the end of statement with a semi-colon like C & Pascal. Brackets signify either to "{" begin a group of statements, or "}" end a group of statements. The // designates a comment. Anything after two slashes the compiler ignores. Now we're ready to read input from the keyboard. Pay attention to the comments, they help explain the programs.
Example II.
import java.io.*; //include Java's standard Input and Output routines

class Echo {
  public static void main (String[] args) throws IOException {

    // Defines the standard input stream
    BufferedReader stdin = new BufferedReader
      (new InputStreamReader(System.in));
    String message; // Creates a varible called message for input

    System.out.print ("Enter the message : ");
    System.out.flush(); // empties buffer, before you input text
    message = stdin.readLine();

    System.out.print("You ");
    System.out.println("entered : " + message);

  } // method main
} // end of class Echo
You have just learned the standard way of getting text. First you create a reader, and then you input the text with readLine() , and finally you use the print command to output it. Notice the difference in the print commands : println prints, then goes to the next line, while print does not. The throws IOException in main lets Java know what to do with errors, when it encounters them.