1. Running Example Programs in Windows

These web notes include many example programs. Run them and play with them. To learn programming, fiddle around with example programs and then write some of your own. This chapter shows how to do this in a bare-bones Windows environment.

Question 1:
Is it sometimes beneficial to type in a program rather than just copying it?

Source: Bradley Kjell, http://programmedlessons.org/Java9/chap07/ch07_01.html
This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 License.

2. Notes

Answer
Yes — sometimes typing in a program forces you to see details you would otherwise miss. 
 Other times it is a waste of effort. Of course, not running the program at all is a 
 supreme waste of opportunity.

Question 2:
Can Microsoft Word be used as a program editor?

3. Step 1: Start Windows Explorer

Answer:
Start Explorer by clicking on the folder icon in the taskbar at the bottom of the screen.

Step 1: Start Windows Explorer

Left-click on the little folder icon. File Explorer should start up.

(Alternative: click on the window icon at the very bottom left and look for the File Explorer icon.)

Exactly what you see depends on what you have previously done with Explorer. If you last used Explorer with the folder you use for programs, it will start up showing that folder.

You may see something like the above. You will have to "navigate" to the disk folder that holds your Java programs.

Click on various icons until you see the root (the top) of your hard disk.

Question 4:
What is the name of your hard disk?

4. Step 2: Navigate

Answer:
Usually you want Java programs in a folder on the hard drive C:

Step 2: Navigate

Left-click on C: in the left panel of the Explorer window. (You can also left-click on a USB drive if you have one plugged in.)

You will see something like the above. A view of files and folders is in the right panel. You can click on one of them to go into it, or make a new folder.

To make a new folder, RIGHT-click on C: then move the mouse pointer over NEW and then FOLDER.

You should have a new folder (subdirectory). Double LEFT-Click on it.

The contents of the folder is displayed in the right panel of Explorer. The folder will be empty if you just created it.

It may take several tries to get this far if you are not familiar with Windows operations.

Question 5:
How do you start a command window for the folder?

5. Step 3: Start a command window and Notepad

Answer:
SHIFT-right-click in the right panel

Step 3: Start a command window and Notepad

Put the mouse cursor in the right panel of the Explorer window. Make sure no file names are highlighted. Left-click in a blank space in the window to un-highlight any file. (If you just created the folder, there will be no files, so this is not needed.)

SHIFT-RIGHT-click in the window.

A menu will pop up. Click on "Open Power-shell window here". (Depending on your revision of Windows, this may be some other similar command window.)

The command prompt is the part PS C:\JavaSource>

In this minimalist environment, you enter commands to the OS by typing them after this prompt. To start Notepad, type notepad after the prompt. Hit "enter".

Question 6:
What is the clipboard in Windows?

6. Step 4: Copy the program into the clipboard

Answer:
The clipboard in Windows (and other GUI environments) is a utility that allows you to copy 
 from one program (like a web browswer) and paste into another (like Notepad.)

Step 4: Copy the program into the clipboard

Copy the program from the Web browser into the clipboard.

You very likely have done this before by copying between Word documents or copying from the web into Word or other programs. This is the same. Copy the program (below) into the clipboard, then paste into Notepad.

Here is the example program, again:

public class HelloPlanets
{
  public static void main ( String[] args )
  {
    String[] planets = {"Mercury", "Venus",  "Earth",   "Mars", "Jupiter", 
                        "Saturn",  "Uranus", "Neptune", "Pluto"};
  
    for ( int j=0; j< planets.length; j++ )
    {
      System.out.println("Hello " + planets[j] +"!" );
    }
  }

}

Highlight the program by clicking the mouse on the first character, and dragging to the last character:

1. In the browser window (this window), put the mouse pointer on the "p" of "program".
2. Push down on the left mouse button. Without lifting up on the mouse button, drag down until the final "}" of the program is covered.
3. Lift up on the mouse button.
4. Put the mouse pointer into the highlighted program.
5. RIGHT-click.
6. Select "Copy". (Or hit control-C)

Be careful not to click the mouse again in the window or you will cancel your selection. (But you can always start over.) After you have done this, you should see something like the following:

Question 7:
Could you paste what you just copied into Notepad?
Could you paste what you just copied into Notepad++?
Could you paste what you just copied into BlueJ?

7. Step 5: Paste into Notepad

Answer
Yes.
If you are using some other text editor (such as Notepad++) or an IDE (such as BlueJ) you can paste into it.

Question 2:
How do you save the text in Notepad to a file?

8. Step 6: Save the Source File

Answer
Use the "Save As" menu option.

Question 9:
Hopefully, the file HelloPlanets.java has been saved to the folder C:\Temp, the same 
 one that the command prompt window is using. How can you confirm that this indeed happened?

9. Step 7: Compile the Program

Answer
Click in the command window and enter the DIR command.

javac HelloPlanets.java

Question 10:
Are we there yet?

10. Step 7: Run the Program

Answer
You need to run the program. That is the point of all this.

Step 7: Run the Program

Enter the command

java HelloPlanets

to run the program. Actually, java starts the Java virtual machine, which then reads in the file of bytecode HelloPlanets.class, which the virtual machine starts executing.

Warning: The command is java with no "c" at the end.

Warning: Use the filename HelloPlanets with no ".class" at the end.

Well, that is one way to do it. Experienced users of Windows will be familiar with most of the steps. They will have found this process fairly easy. If you did not, it is merely a matter of practice (or finding a friend.)

Question 10:
Is Pluto a planet?

11. End of the Chapter

Answer
Once it was classified as a planet, and the program was correct.
Now, it is not, and the program is not correct.