CMPU 102, Spring 2017
 Lab 1: Solving Problems with DrJava
  

 Lab assignment in 3 parts

 Part I: MODIFYING AN EXISTING PROGRAM

    1.  Log in to your Vassar CS account. You should see your Desktop.

    2.  Create a cs102 directory and then change control into that
        directory. If you are in a terminal, type the following:

          mkdir cs102
          cd cs102

    3.  Create a new directory for lab 1 by entering:

          mkdir lab1

    4.  Open the directory you created in the last step by entering:

          cd lab1

    5.  Open the web browser from the menu called Internet at the bottom
        left corner of the screen.

    6.  Go to the course web pag and download the file AddABCDv1.java     
        program from the course web page, Labs section, into your 
        cs102/lab1 directory.  

    7.  Open the DrJava integrated development environment (IDE) by choosing 
        DrJava from the Programming menu.

    8.  Open the AddABCDv1.java file in DrJava. Make sure the class 
        name inside the file matches the prefix of the filename exactly 
        (take note that upper and lower case characters in the name).

    9. Compile and then run the file using the buttons at the top of the
       DrJava window. The file should compile with no syntax errors 
       initially.  

   10. Read the comments in the AddABCDv1.java file and make the changes 
       marked as "TASKS".  Save, compile, and run the file when you are 
       finished making each change.



Part II: Getting input from the keyboard using the javax.swing.JOptionPane 
         class.

   --------------------------------------------------------------------

    A fancier way to get input from the user is by using a class from 
    another java package: javax.swing. The class and method we want to 
    use from the javax.swing package creates a pop-up window for entering 
    data and, without an import statement, the showInputDialog method is 
    called as shown below:

    String x = javax.swing.JOptionPane.showInputDialog("Please enter x:");

    The javax.swing part of the line above is the package that the 
    JOptionPane class is written in and is called the "fully qualified
    name". 

    Open the Interactions window of DrJava and copy the line above at the 
    prompt. When you press return, a pop-up box should open, with a 
    input area. Type something in the box and then type a value for x 
    at the prompt. You should see the text the user entered in the pop-up 
    box.

    If you import javax.swing.* in a file, you can use the shorter version 
    to read the data as shown below:

       String x = JOptionPane.showInputDialog("Please enter x:");

    ---------------------------------------------------------------------

    1. Save AddABCDv1.java as AddABCDv2.java and change the class name
       in the AddABCDv2.java file to match the file name. Import the
       package necessary to use the JOptionPane class instead of the 
       import for the Scanner class.

    2. Use the showInputDialog method of the JOptionPane class to prompt 
       for and store each String (you should use 4 separate calls to the 
       showInputDialog method to obtain the inputs from the user for 
       tempA, tempB, tempC, and tempD). Use "Enter value a: ", etc. as 
       the argument to showInputDialog.

    3. Print the sum using the showMessageDialog method of the JOptionPane
       class. The first argument to this method is null.

    4. Try to decipher the errors on your own and then ask your lab 
       instructor or a coach for help figuring out the syntax errors if 
       necessary. 

    NOTE: EVERY OPEN CLASS IN DRJAVA WILL SHOW UP ON THE LEFT SIDE MENU.
    PRESSING COMPILE AFFECTS EVERY ONE OF THEM.  SO DON’T HAVE ANY FILES
    WITH SYNTAX ERRORS OPEN.
    



Part III: Write a Java program from scratch.

    1. Create a new class called StringFun in DrJava and name the file as
       StringFun.java

    2. Inside the main method, declare 4 String variables, giving each 
       variable a name of your choosing (make sure the names obey the 
       conventions for variable names).

    3. Use the showInputDialog method of the JOptionPane class to prompt 
       for and store each String (you should use 4 separate calls to the 
       showInputDialog method to obtain the strings). Try to make the prompt 
       for input clear in the call to showInputDialog, e.g., "Enter the first 
       string: ", "Enter the second string: ", etc.

       Import any packages required to use the JOptionPane class or use 
       the fully qualified name of this class in your program.

    4. Look up the 2-parameter showMessageDialog method in the Java API. This
       method requires 2 arguments, the first is a parent component and the 
       second a String. In this program, the parent component should be the
       keyword null.  

       To make your output a little neater, insert a " " (blank space)
       between each entry when it is displayed, Use the + operator to
       concatenate the Strings in the output correctly.

       For example, if I entered the strings "I", "like", "Java", and "most"
       for tempA, tempB, tempC, and tempD, the display in the 
       JOptionPane.showMessageDialog method would be:

              "I like Java most."

        in a pop-up dialog box.

    5.  Be sure to put your name and a description of what the file does 
        in comments at the top of this file. 

    Run all programs for your instructor or a coach to get credit for this 
    lab.  Also, go to the 102 Moodle site and submit a folder containing
    all lab files at the “submit lab 1” link.

BE SURE TO HAVE A COACH OR YOUR PROFESSOR CHECK YOUR NAME OFF ON THE LAB 
ROSTER AS HAVING COMPLETED THE LAB.