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1. In the SimpleStamperPanel example from Subsection 6.4.2, a rectangle or oval is drawn on

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the panel when the user clicks the mouse, except that when the user shift-clicks, the panel

is cleared instead. Modify this class so that the modified version will continue to draw

figures as the user drags the mouse. That is, the mouse will leave a trail of figures as the

user drags the mouse. However, if the user shift-clicks, the panel should simply be cleared

and no figures should be drawn even if the user drags the mouse after shift-clicking. Use

your panel either in an applet or in a stand-alone application (or both). Here is a picture

of my solution:

The source code for the original panel class is SimpleStamperPanel.java. An applet

that uses this class can be found in SimpleStamperApplet.java, and a main program that

uses the panel in a frame is in SimpleStamper.java. See the discussion of dragging in

Subsection 6.4.4. (Note that in the original version, I drew a black outline around each

shape. In the modified version, I decided that it would look better to draw a gray outline

instead.)

2. Write a panel that shows a small red square and a small blue square. The user should be

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able to drag either square with the mouse. (You’ll need an instance variable to remember

which square the user is dragging.) The user can drag the square o the applet if she

wants; if she does this, it’s gone. Use your panel in either an applet or a stand-alone

application.

3. Write a panel that shows a pair of dice. When the user clicks on the panel, the dice should

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be rolled (that is, the dice should be assigned newly computed random values). Each die

should be drawn as a square showing from 1 to 6 dots. Since you have to draw two dice,

its a good idea to write a subroutine, “void drawDie(Graphics g, int val, int x,

int y)”, to draw a die at the specified (x,y) coordinates. The second parameter, val,

specifies the value that is showing on the die. Assume that the size of the panel is 100

by 100 pixels. Also write an applet that uses your panel as its content pane. Here is a

picture of the applet:

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4. In Exercise 6.3, you wrote a pair-of-dice panel where the dice are rolled when the user

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clicks on the panel Now make a pair-of-dice program in which the user rolls the dice by

clicking a button. The button should appear under the panel that shows the dice. Also

make the following change: When the dice are rolled, instead of just showing the new

value, show a short animation during which the values on the dice are changed in every

frame. The animation is supposed to make the dice look more like they are actually rolling.

Write your program as a stand-alone application.

5. In Exercise 3.6, you drew a checkerboard. For this exercise, write a checkerboard applet

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where the user can select a square by clicking on it. Hilite the selected square by drawing

a colored border around it. When the applet is first created, no square is selected. When

the user clicks on a square that is not currently selected, it becomes selected. If the user

clicks the square that is selected, it becomes unselected. Assume that the size of the applet

is exactly 160 by 160 pixels, so that each square on the checkerboard is 20 by 20 pixels.

6. For this exercise, you should modify the SubKiller game from Subsection 6.5.4. You can

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start with the existing source code, from the file SubKillerPanel.java. Modify the game

so it keeps track of the number of hits and misses and displays these quantities. That

is, every time the depth charge blows up the sub, the number of hits goes up by one.

Every time the depth charge falls o the bottom of the screen without hitting the sub, the

number of misses goes up by one. There is room at the top of the panel to display these

numbers. To do this exercise, you only have to add a half-dozen lines to the source code.

But you have to figure out what they are and where to add them. To do this, you’ll have

to read the source code closely enough to understand how it works.

7. Exercise 5.2 involved a class, StatCalc.java, that could compute some statistics of a set of

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numbers. Write a program that uses the StatCalc class to compute and display statistics

of numbers entered by the user. The panel will have an instance variable of type StatCalc

that does the computations. The panel should include a JTextField where the user enters

a number. It should have four labels that display four statistics for the numbers that have

been entered: the number of numbers, the sum, the mean, and the standard deviation.

Every time the user enters a new number, the statistics displayed on the labels should

change. The user enters a number by typing it into the JTextField and pressing return.

There should be a “Clear” button that clears out all the data. This means creating a new

StatCalc object and resetting the displays on the labels. My panel also has an “Enter”

button that does the same thing as pressing the return key in the JTextField. (Recall that

a JTextField generates an ActionEvent when the user presses return, so your panel should

register itself to listen for ActionEvents from the JTextField.) Write your program as a

stand-alone application. Here is a picture of my solution to this problem:

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Exercises

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