Computer Science I

Creating a color using java's Color class constructor (specifying red, green, and blue values):

> Color color = new Color(130,45,92);  /* red = 130, green = 45, blue = 92 */

Creating and showing a Picture using the text's FileChooser:

> String fileName = FileChooser.pickAFile();
> Picture p = new Picture(fileName);
> p.show();  /* display the picture */

Creating and playing a Sound:

> String fileName = FileChooser.pickAFile();
> Sound s = new Sound(fileName);
> s.play();  /* play the sound */

Arrays in Java

int[] arr;    /* arr is (null) reference to an int array */

int[10] arr;   /* arr references a 10-element int array */

int[] arr = new int[5];  /* arr references a five-element array */

int[] numbers = {1,2,3,4};   /* declaration and initialization */

Color[] colors = new Color[3];  /* colors references a 3-element array */
                                /* each element is null */
colors[0] = new Color(0,0,0);
colors[1] = Color.RED;
colors[2] = ColorChooser.pickAColor();

Using the for each statement to sum the elements of an array:

int[] arr = {10, 20, 30, 40, 50};

int sum = 0;

for (int value : arr)
{
   sum = sum + value;
}

Using a while statement to sum the elements of an array:

int[] arr = {10, 20, 30, 40, 50};

int sum = 0;

int index = 0;  /* starting subscript for an array */

while (index < arr.length)
{
   sum = sum + arr[index];
   index++;
}

Getting and setting the color of a pixel:

Pixel p;  /* assume p gets initialized somehow */

p.setColor(Color.RED);

Color c = p.getColor();

Getting and setting the red component of a pixel (similar methods for green and blue):

int redValue = p.getRed();

p.setRed(200);

Getting the pixels from a picture:

String fileName = FileChooser.pickAFile();
Picture p = new Picture(fileName);

Getting an individual pixel in row 4, column 12:

Pixel pix = p.getPixel(4, 12);

Getting all the pixels from a picture:

Pixel[] pixels = p.getPixels();

Processing all pixels with a for each statement:

for (Pixel pix : pixels)
{
    /* do something with pix */
}

Setting each pixel's red component:

for (Pixel pix : pixels)
{
    pix.setRed(200);
}

Repainting a picture p:

p.repaint();

Exploring a picture p:

p.explore();

while statement examples:

int [] arr;

/* assume arr is initialized somehow ... */

int sum = 0;
int index = 0;

/* sum the elements of arr */
while (index < arr.length)
{
   sum = sum + arr[index];
   index++;
}

/* sum the odd-numbered elements (1, 3, 5, ...) of arr */

int sum = 0;
int index = 0;

while (index < arr.length)
{
   sum += arr[index];
   index = index + 2;
}

for statement examples:

int [] arr;

/* assume arr is initialized somehow ... */

int sum = 0;

/* sum the elements of arr */
for (int index = 0; index < arr.length; index++)
{
   sum = sum + arr[index];
}

/* sum the odd-numbered elements (1, 3, 5, ...) of arr */

int sum = 0;

for (int index = 0; index < arr.length; index+=2)
{
   sum = sum + arr[index];
}

Reversing the elements of an array

Reversing the pixels in a Picture

Exam 1 will be given on Friday, September 22

LAB 5 POSTPONED UNTIL NEXT WEEK!!!

Exam 2
Exam 2 solution   pdf