Objectives:

• Learn how to incorporate a prewritten package into your project. (Exercise I).
• Use the simpleIO package to provide input via menus. (Exercise II).
• Use simple selection to access alternatives (Exercise III).

The second and third parts will be based on a variation of the Button class that was developed during the lecture. You should think about how you are going to do Exercise III before coming into the lab. Note: You can save time by viewing the laboratory instructions in the browser and cutting and pasting code in. However, you should look carefully at the code and make sure that you understand it before coming to the lab. You can ask in the lab or the lecture if you don't understand it.

Check-off procedure:

Be sure to bring your copy of A Beginner's Guide to Java WorkShop 3.0: http://vip.cs.utsa.edu/classes/JavaInfo/JavaWorkShop.html You must attend the recitation and sign in. You are considered to be checked off if you make a reasonable effort to complete the lab. You should try to have done most of this lab prior to lab time.

Laboratory details:

• Exercise I: The Warm Up
  • Bring up Java WorkShop.

  • Make sure that only the default portfolios show in the Navigation Window.

  • Work through the example in the Beginner's Guide to Java Workshop Adding a prewritten package. This example uses the simpleIO package from the textbook to provide simple I/O.

    Notes: If you are working at home, you will need to download the .java files for simpleIO into a directory on your hard drive (say c:\savework\jws\simpleIO). The path for simpleIO in the labs is as follows:

    • In the student computing facilities: j:\krobbins\1711
    • In the teaching labs: x:\1711 where you have mapped \\coblab2\classes to the x: drive.
    • In the help sessions in 3.02.04SB: c:\WINNT\Profiles\MIIGuest\jws

• Exercise II: Accessing a Button Through a GUI
  • Create a new portfolio called ButtonGUI.

  • Create a new standalone project in the ButtonGUI portfolio called ButtonGUIMain containing the following code:

    public class ButtonGUIMain {
    
        /**
         * Constructor.
         */  
        public ButtonGUIMain () {
        }
    
        public static void main(String args[]) {
                  // Create a menu for entering selections and test it out.
            ButtonGUI myButtonMenu = new ButtonGUI();
            int myPick = myButtonMenu.MakeSelection("Button A");
            System.out.println("I picked " + myPick);
            myPick = myButtonMenu.MakeSelection("Button B");
            System.out.println("I picked " + myPick);
    
                 // Create a button and use myButtonMenu to push or clear it.
            Button myButton = new Button();
            myPick = myButtonMenu.MakeSelection("Push or clear myButton:");
            if (myPick == 0)
                myButton.ClearButton();
            else if (myPick == 1)
                myButton.PushButton();
            System.out.println("myButton is pushed? " + myButton.AmIPushed());
        }
    }
    

  • Create a new file that contains the following code:

    import java.util.*;
    
    public class Button {
    
        // fields (data)
        private boolean myIamPushed;
        private Date myCreationDate;
    
        // constructor
        public Button () {
            myIamPushed = false;
            myCreationDate = new Date();
        }
    
        // accessor methods
        public boolean AmIPushed(){
            return myIamPushed;
        }
    
        public String GetWhenMade() {
            return myCreationDate.toString();
        }
    
        // modifier methods
        public void ClearButton() {
            myIamPushed = false;
        }
    
        public void PushButton() {
            myIamPushed = true;
        }
    
    }
    
    

    Save the file as Button.java in the same directory as ButtonGUIMain. This should be the default. Add the Button.java file to the ButtonGUIMain project.

  • Create a new file containing the following code:

    import simpleIO.*;
    
    public class ButtonGUI extends SimpleGUI {
    
        // field (data)
        private int myCurrentChoice;
    
        // constructor
        public ButtonGUI() {
            super();            // make sure superclass constructor is called
            createMenu();       // create a menu window
            addChoice("Clear");   // add menu option 0 with prompt "Clear"
            addChoice("Push");    // add menu option 1 with prompt "Push"
            myCurrentChoice = 0;
        }
    
        // accessor method
       public int GetCurrentChoice() {
           return myCurrentChoice;
       }
    
        // modifier method
        public int MakeSelection(String menuName) {
           myCurrentChoice = getChoice(menuName);
           return myCurrentChoice;
        }
    }
    

    Save the file as ButtonGUI.java in the same directory as ButtonGUIMain. This should be the default. Add the ButtonGUI.java file to the ButtonGUIMain project.

  • Add the root directory for the simpleIO package to the CLASSPATH for the project.

  • Build and run the project. If you have bugs, you'll need to fix them.

  • Trace through the program and make sure that you understand the output.

• Exercise III: Using Simple Section to Access Alternatives
  • Add code to ButtonGUIMain (about 7 lines):
    • Create two buttons, with variable names waterButton and changeButton.
    • Use ButtonGUI to ask the user to press or clear waterButton.
    • If ButtonGUI is pushed, print a message at the console that the waterButton was pushed.
    • If ButtonGUI is cleared, use ButtonGUI to ask the user to press or clear changeButton.
    • Print a message the console indicating whether or not the changeButton was pushed.

     

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    Last revision: September 22, 1999 at 12:40 pm.