Objectives:

• Learn to manipulate arrays of objects.
• Have more extensive practice with loops.
• Use object composition (the has-a relationship).
• Use method overloading.

Check-off procedure:

You must attend the recitation and sign in. This laboratory will be checked off using the new procedures.

Laboratory details:

In this project you will be working with and testing a class called VButtonPanel that has an array of buttons and methods for accessing them. The VButtonPanel is created by specifying an array of strings that contain the names of the buttons.

Part I: The Warm Up

Create a new standalone project called VPanelButtonMain. In addition to the main program (VPanelButtonMain.java), the project includes the classes defined in VButton.java and VButtonPanel.java given below. These should be available in the lab for you to copy into your savework directory. You should build and run this project and make sure that you understand how the classes work before proceeding.

• VButton.java:

  import java.util.*;
  
  public class VButton {
  
      // fields (data)
      private boolean myIamPushed;
      private Date myCreationDate;
      private String myName;
  
      // constructor
      public VButton (String name) {
          myIamPushed = false;
          myCreationDate = new Date();
          myName = new String(name);
      }
  
      // accessor methods
      public boolean amIPushed(){
          return myIamPushed;
      }
  
      public String getName() {
          return myName;
      }
  
      public String getWhenMade() {
          return myCreationDate.toString();
      }
  
      public String toString() {
         String state;
         if (amIPushed())
            state = "pushed";
         else   
            state = "cleared";
         return myName + ": created " + myCreationDate + " is " + state;
      }
  
      // modifier methods
      public void clearButton() {
          myIamPushed = false;
      }
  
      public void pushButton() {
          myIamPushed = true;
      }
  }
  

• VButtonPanel.java:

  public class VButtonPanel {
  
      // field (data)
      private VButton [] myButtons; 
  
      // constructor
      public VButtonPanel(String bnames []) {
          myButtons = new VButton[bnames.length];
          for (int k = 0; k < bnames.length; k++) {
              myButtons[k] = new VButton(bnames[k]); 
          }
      }
  
      // accessors
      public void printPanel() {  // Exercise I 
        // Output this panel to the console 
        System.out.println("The button panel will be printed out here");
      } 
  
      public boolean buttonPushed(int i) { // Exercise II 
         // Add code to return true if button i in myButtons is pushed.
         // If i is not in range return false or button is not pushed, return false.
         return false;
      }
  
      // modifiers
      public void pushButton(int i) { // Exercise II
        // Add code to push button i in myButtons.  Make sure i is in range. 
      }
  
      public void clearButton(int i) { // Exercise II
        // Add code to clear button i in myButtons. Make sure i is in range.
      }
  
      public void pushAllButtons() {  // Exercise II
         //Add code to push all of the buttons in myButtons.
      }
  
      public void clearAllButtons() { // Exercise II
         //Add code to clear all of the buttons in myButtons.
      }
  }
  

• VButtonPanelMain:

  public class VButtonPanelMain {
  
      /**
       * Constructor.
       */  
      public VButtonPanelMain () {
      }
  
      public static void main(String args[]) {
                  // make a test array with strings for naming the buttons
          String [] someNames = {"Water", "Juice", "Cola", "Orange", "RootBeer"};
          VButtonPanel panel = new VButtonPanel(someNames);
          panel.printPanel();
      }
  }
  

Exercise I: Adding output method for debugging

• Add code in printPanel() to print out the VButtonPanel. Output each button in myButtons on a separate line by calling the corresponding button's toString method.
• Build and test.
• Add additional statements to the main program to create another VButtonPanel object that holds 3 buttons named: "Popcorn", "Peanuts", and "Raisins".
• Add additional statements to the main program to test the new button.
• Build and run.

Exercise II: Adding basic accessor and modifier methods

• Add code to implement the pushButton, clearButton and buttonPushed methods of VButtonPanel
• Add statements in the main program to test the new methods.
• Build and run.
• Add code to implement the pushAllButtons and clearAllButtons.
• Build and run.
• Add statements in the main program to test the new methods.
• Build and run.

Exercise III: Locating a particular button in the panel

• Add the following accessor method to VButtonPanel:

  public int getIndex(String name) {
    // return the position of the button called buttonName in the array myButtons
    // or -1 if it is not in myButtons
  }
  

• Add test statements to the main program to test the getIndex.
• Build and run.

Exercise IV: Overloading the accessor and modifier methods

A user may want to access a button by its position, but more likely will want to access it by name. Add the following methods to VButtonPanel class to allow access by name. These methods have the same names as ones already in the class. The methods are said to be overloaded.

• public void pushButton(String name)
• public void clearButton(String name)
• public boolean buttonPushed(String name)

Build and run the program. Add additional test statements to the main program. Create a button panel object with 10 buttons in it to test.