Questions about PuzzleModel, PuzzleView/Gui, PuzzleController

1. The following method is part of PuzzleGui, this method is called as part of the initialization of that class. Explain the purpose of the method (do a best guess based on the names of the parameters and variables).

   
       private void constrainResize()
       {
          addComponentListener(new ComponentAdapter(){
   		public void componentResized(ComponentEvent e)
   		{
   		    int w = getWidth();
   		    int h = getHeight();
   		    w = Math.max(w,h);
   		    setSize(w,w);
   		}
   	    });
   
       }
   
   

2. In the PuzzleGui class the private instance variable myUndo is of type JMenuItem. Here's the code that initializes this variable. In broad terms, explain each major part of this initialization.

   	myUndo = new JMenuItem(new AbstractAction("Undo")
   	    {
   		public void actionPerformed(ActionEvent e) {
   		    myControl.undoMove();
   		}
   	    });
   	setEnabledUndo(false);
   	menu.add(myUndo);
   

3. The code below creates moveMaker, an object which is attached to each of the n² JButtons in a PuzzleGui view that's the view of an n x n puzzle. Why is it possible to share the same object among all the buttons, e.g., rather than using a different button-specific listener for each button? (explain what happens when a button is pressed based on the code below).

     ActionListener moveMaker = new ActionListener(){
            public void actionPerformed(ActionEvent e)
            {
               int val = Integer.parseInt(e.getActionCommand());
               myControl.makeMove(new PuzzleMove(val));
            }
     };
   
   

4. The code below from PuzzleModel makes a move in the model. Explain based on best-guess information (based on the names of the methods and variables) the purpose of the statements in the scope of the if statement that calls isNeighbors. Note: the instance field myList stores all moves for the purpose of undo.

   
       private boolean doMove(PuzzleMove move, boolean doStore)
       {
           int index = getIndex(move.getValue());
           int blankIndex = getIndex(getBlankValue());
   	
           if (isNeighbors(index,blankIndex)) {
              int temp = myNumbers[blankIndex];
              myNumbers[blankIndex] = myNumbers[index];
              myNumbers[index] = temp;
              myControl.showBoard(myNumbers);
              if (doStore){
                  myList.add(move);
              }
              return true;
          }
          return false;	
       }
   

5. The code below is from PuzzleModel. Explain each line of this function. The instance variable myList is of type java.util.LinkedList rather than ArrayList because the latter field doesn't have a method removeLast.

       /**
        * Undoes the last move (if there is one) and returns true iff
        * another undo is possible
        * @return true if another undo is possible, else returns false
        */
       public boolean undo()
       {
           if (myList.size() != 0) {
              doMove((PuzzleMove) myList.removeLast(),false);
           }
           return myList.size() > 0;
       }