Blobs (applet)
import java.awt.event.*;
import java.applet.Applet;
public class Blobs extends Applet implements ActionListener, MouseListener {
final static int SQUARE_SIZE = 8; // Size of one square in the grid.
Label message; // For displaying information to the user.
Choice percentFill; // When the user clicks the "New Blobs" button
// to randomly fill the grid, this menu controlls
// the probability that a given square in the grid
// is filled.
int rows; // Number of rows in the grid. This depend on the size of the applet.
int columns; // Number of columns in the grid. This depend on the size of the applet.
boolean[][] filled; // filled[r][c] is true if the square at row r, column c is filled.
boolean[][] visited; // visited[r][c] is true if the square at row r, column c has
// has already been visited by the getBlobSize() method.
public void init() {
// Initialize the applet. Use a null layout and set the bounds
// of the components in the applet directly. The applet listens
// for mouse clicks on itself.
setLayout(null);
setBackground(new Color(220,220,255));
addMouseListener(this);
/* Determine the number of rows and columns and create the
filled and visited arrays. Fill the squares at random. */
int width = getSize().width;
int height = getSize().height;
rows = (height - 100) / SQUARE_SIZE;
columns = (width - 20) / SQUARE_SIZE;
filled = new boolean[rows][columns];
visited = new boolean[rows][columns];
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++)
filled[r][c] = (Math.random() < 0.3);
/* Create the components. */
message = new Label("Click a square to get the blob size.", Label.CENTER);
message.setForeground(Color.blue);
message.setFont(new Font("Helvetica",Font.PLAIN,14));
percentFill = new Choice();
percentFill.add("10% fill");
percentFill.add("20% fill");
percentFill.add("30% fill");
percentFill.add("40% fill");
percentFill.add("50% fill");
percentFill.add("60% fill");
percentFill.add("70% fill");
percentFill.add("80% fill");
percentFill.add("90% fill");
percentFill.setBackground(Color.white);
percentFill.select(2);
Button newButton = new Button("New Blobs");
newButton.addActionListener(this);
newButton.setBackground(Color.lightGray);
Button countButton = new Button("Count the Blobs");
countButton.addActionListener(this);
countButton.setBackground(Color.lightGray);
/* Add the components to the applet and set their sizes and positions. */
add(message);
add(newButton);
add(percentFill);
add(countButton);
message.setBounds(15, height-75, width-30, 18);
countButton.setBounds(15, height-50, width-30, 18);
newButton.setBounds(15, height-25, (width-40)/2, 18);
percentFill.setBounds(width/2 + 5, height-25, (width-40)/2, 18);
} // end init();
public void paint(Graphics g) {
// Paint the applet, showing the grid of squares.
int width = getSize().width;
int height = getSize().height;
/* Draw a blue border around the applet. */
g.setColor(Color.blue);
g.drawRect(0,0,width-1,height-1);
g.drawRect(1,1,width-3,height-3);
/* Fill the area occupied by the grid with white, then draw
black lines around this area and between the squares of
the grid. */
g.setColor(Color.white);
g.fillRect(10, 10, columns*SQUARE_SIZE, rows*SQUARE_SIZE);
g.setColor(Color.black);
for (int i = 0; i <= rows; i++)
g.drawLine(10, 10 + i*SQUARE_SIZE, columns*SQUARE_SIZE + 10, 10 + i*SQUARE_SIZE);
for (int i = 0; i <= columns; i++)
g.drawLine(10 + i*SQUARE_SIZE, 10, 10 + i*SQUARE_SIZE, rows*SQUARE_SIZE + 10);
/* Fill "visited" squares with red and "filled" squares with gray.
Other squares remain white. */
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++) {
if (visited[r][c]) {
g.setColor(Color.red);
g.fillRect(11 + c*SQUARE_SIZE, 11 + r*SQUARE_SIZE, SQUARE_SIZE - 1, SQUARE_SIZE - 1);
}
else if (filled[r][c]) {
g.setColor(Color.gray);
g.fillRect(11 + c*SQUARE_SIZE, 11 + r*SQUARE_SIZE, SQUARE_SIZE - 1, SQUARE_SIZE - 1);
}
}
} // end paint();
public void actionPerformed(ActionEvent evt) {
// When the user clicks a button, call the appropriate method.
String cmd = evt.getActionCommand();
if (cmd.equals("New Blobs"))
fillGrid();
else if (cmd.equals("Count the Blobs"))
countBlobs();
}
void fillGrid() {
// When the user clicks the "New Blobs" button, fill the grid of squares
// randomly. The probability that a given square is filled is given by
// the percentFill Choice menu. The probabilities corresponding to the
// items in that menu are 0.1, 0.2,... 0.9. The visited array is cleared
// so there won't be any red-colored squares in the grid.
double probability = (percentFill.getSelectedIndex() + 1) / 10.0;
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++) {
filled[r][c] = (Math.random() < probability);
visited[r][c] = false;
}
message.setText("Click a square to get the blob size.");
repaint();
}
void countBlobs() {
// When the use clicks the "Count the Blobs" button, find the number
// of blobs in the grid and report the number in the message Label.
int count = 0; // Number of blobs.
/* First clear out the visited array. The getBlobSize() method will
mark every filled square that it finds by setting the corresponding
element of the array to true. Once a square has been marked as
visited, it will stay marked until all the blobs have been counted.
This will prevent the same blob from being counted more than once. */
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++)
visited[r][c] = false;
/* For each position in the grid, call getBlobSize() to get the size
of the blob at that position. If the sixe is not zero, count a blob.
Note that if we come to a position that was part of a previously
counted square, getBlobSize() will return 0 and the blob will not
be counted again. */
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++) {
if (getBlobSize(r,c) > 0)
count++;
}
repaint(); // Note that all the filled squares will be red!
message.setText("The number of blobs is " + count);
} // end countBlobs()
int getBlobSize(int r, int c) {
// Counts the squares in the blob at position (r,c) in the
// grid. Squares are only counted if they are filled and
// unvisited. If this routine is called for a position that
// has been visited, the return value will be zero.
if (r < 0 || r >= rows || c < 0 || c >= columns) {
// This position is not in the grid, so there is
// no blob at this position.
return 0;
}
if (filled[r][c] == false || visited[r][c] == true) {
// This square is not part of a blob, or else it has
// already been counted, so return zero.
return 0;
}
visited[r][c] = true; // Mark the square as visited so that
// we won't count it again during the
// following recursive calls to this method.
int size = 1; // Count the square at this position, then count the
// the blobs that are connected to this square
// horizontally or vertically.
size += getBlobSize(r-1,c);
size += getBlobSize(r+1,c);
size += getBlobSize(r,c-1);
size += getBlobSize(r,c+1);
return size;
} // end getBlobSize()
public void mousePressed(MouseEvent evt) {
// The user has clicked the mouse on the applet. If the
// user has clicked on a position in the grid, count
// the number of squares in the blob at that position.
int row = (evt.getY() - 10) / SQUARE_SIZE;
int col = (evt.getX() - 10) / SQUARE_SIZE;
if (row < 0 || row >= rows || col < 0 || col >= columns) {
message.setText("Please click on a square!");
return;
}
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++)
visited[r][c] = false; // Clear visited array before counting.
int size = getBlobSize(row,col);
if (size == 0)
message.setText("There is no blob at (" + row + "," + col + ").");
else if (size == 1)
message.setText("The blob at (" + row + "," + col + ") contains 1 square.");
else
message.setText("The blob at (" + row + "," + col + ") contains " + size + " squares.");
repaint();
}
public void mouseReleased(MouseEvent e) { } // Methods required by MouseListener interface
public void mouseClicked(MouseEvent e) { }
public void mouseEntered(MouseEvent e) { }
public void mouseExited(MouseEvent e) { }
} // end class Blobs
import java.awt.event.*;
import java.applet.Applet;
public class Blobs extends Applet implements ActionListener, MouseListener {
final static int SQUARE_SIZE = 8; // Size of one square in the grid.
Label message; // For displaying information to the user.
Choice percentFill; // When the user clicks the "New Blobs" button
// to randomly fill the grid, this menu controlls
// the probability that a given square in the grid
// is filled.
int rows; // Number of rows in the grid. This depend on the size of the applet.
int columns; // Number of columns in the grid. This depend on the size of the applet.
boolean[][] filled; // filled[r][c] is true if the square at row r, column c is filled.
boolean[][] visited; // visited[r][c] is true if the square at row r, column c has
// has already been visited by the getBlobSize() method.
public void init() {
// Initialize the applet. Use a null layout and set the bounds
// of the components in the applet directly. The applet listens
// for mouse clicks on itself.
setLayout(null);
setBackground(new Color(220,220,255));
addMouseListener(this);
/* Determine the number of rows and columns and create the
filled and visited arrays. Fill the squares at random. */
int width = getSize().width;
int height = getSize().height;
rows = (height - 100) / SQUARE_SIZE;
columns = (width - 20) / SQUARE_SIZE;
filled = new boolean[rows][columns];
visited = new boolean[rows][columns];
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++)
filled[r][c] = (Math.random() < 0.3);
/* Create the components. */
message = new Label("Click a square to get the blob size.", Label.CENTER);
message.setForeground(Color.blue);
message.setFont(new Font("Helvetica",Font.PLAIN,14));
percentFill = new Choice();
percentFill.add("10% fill");
percentFill.add("20% fill");
percentFill.add("30% fill");
percentFill.add("40% fill");
percentFill.add("50% fill");
percentFill.add("60% fill");
percentFill.add("70% fill");
percentFill.add("80% fill");
percentFill.add("90% fill");
percentFill.setBackground(Color.white);
percentFill.select(2);
Button newButton = new Button("New Blobs");
newButton.addActionListener(this);
newButton.setBackground(Color.lightGray);
Button countButton = new Button("Count the Blobs");
countButton.addActionListener(this);
countButton.setBackground(Color.lightGray);
/* Add the components to the applet and set their sizes and positions. */
add(message);
add(newButton);
add(percentFill);
add(countButton);
message.setBounds(15, height-75, width-30, 18);
countButton.setBounds(15, height-50, width-30, 18);
newButton.setBounds(15, height-25, (width-40)/2, 18);
percentFill.setBounds(width/2 + 5, height-25, (width-40)/2, 18);
} // end init();
public void paint(Graphics g) {
// Paint the applet, showing the grid of squares.
int width = getSize().width;
int height = getSize().height;
/* Draw a blue border around the applet. */
g.setColor(Color.blue);
g.drawRect(0,0,width-1,height-1);
g.drawRect(1,1,width-3,height-3);
/* Fill the area occupied by the grid with white, then draw
black lines around this area and between the squares of
the grid. */
g.setColor(Color.white);
g.fillRect(10, 10, columns*SQUARE_SIZE, rows*SQUARE_SIZE);
g.setColor(Color.black);
for (int i = 0; i <= rows; i++)
g.drawLine(10, 10 + i*SQUARE_SIZE, columns*SQUARE_SIZE + 10, 10 + i*SQUARE_SIZE);
for (int i = 0; i <= columns; i++)
g.drawLine(10 + i*SQUARE_SIZE, 10, 10 + i*SQUARE_SIZE, rows*SQUARE_SIZE + 10);
/* Fill "visited" squares with red and "filled" squares with gray.
Other squares remain white. */
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++) {
if (visited[r][c]) {
g.setColor(Color.red);
g.fillRect(11 + c*SQUARE_SIZE, 11 + r*SQUARE_SIZE, SQUARE_SIZE - 1, SQUARE_SIZE - 1);
}
else if (filled[r][c]) {
g.setColor(Color.gray);
g.fillRect(11 + c*SQUARE_SIZE, 11 + r*SQUARE_SIZE, SQUARE_SIZE - 1, SQUARE_SIZE - 1);
}
}
} // end paint();
public void actionPerformed(ActionEvent evt) {
// When the user clicks a button, call the appropriate method.
String cmd = evt.getActionCommand();
if (cmd.equals("New Blobs"))
fillGrid();
else if (cmd.equals("Count the Blobs"))
countBlobs();
}
void fillGrid() {
// When the user clicks the "New Blobs" button, fill the grid of squares
// randomly. The probability that a given square is filled is given by
// the percentFill Choice menu. The probabilities corresponding to the
// items in that menu are 0.1, 0.2,... 0.9. The visited array is cleared
// so there won't be any red-colored squares in the grid.
double probability = (percentFill.getSelectedIndex() + 1) / 10.0;
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++) {
filled[r][c] = (Math.random() < probability);
visited[r][c] = false;
}
message.setText("Click a square to get the blob size.");
repaint();
}
void countBlobs() {
// When the use clicks the "Count the Blobs" button, find the number
// of blobs in the grid and report the number in the message Label.
int count = 0; // Number of blobs.
/* First clear out the visited array. The getBlobSize() method will
mark every filled square that it finds by setting the corresponding
element of the array to true. Once a square has been marked as
visited, it will stay marked until all the blobs have been counted.
This will prevent the same blob from being counted more than once. */
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++)
visited[r][c] = false;
/* For each position in the grid, call getBlobSize() to get the size
of the blob at that position. If the sixe is not zero, count a blob.
Note that if we come to a position that was part of a previously
counted square, getBlobSize() will return 0 and the blob will not
be counted again. */
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++) {
if (getBlobSize(r,c) > 0)
count++;
}
repaint(); // Note that all the filled squares will be red!
message.setText("The number of blobs is " + count);
} // end countBlobs()
int getBlobSize(int r, int c) {
// Counts the squares in the blob at position (r,c) in the
// grid. Squares are only counted if they are filled and
// unvisited. If this routine is called for a position that
// has been visited, the return value will be zero.
if (r < 0 || r >= rows || c < 0 || c >= columns) {
// This position is not in the grid, so there is
// no blob at this position.
return 0;
}
if (filled[r][c] == false || visited[r][c] == true) {
// This square is not part of a blob, or else it has
// already been counted, so return zero.
return 0;
}
visited[r][c] = true; // Mark the square as visited so that
// we won't count it again during the
// following recursive calls to this method.
int size = 1; // Count the square at this position, then count the
// the blobs that are connected to this square
// horizontally or vertically.
size += getBlobSize(r-1,c);
size += getBlobSize(r+1,c);
size += getBlobSize(r,c-1);
size += getBlobSize(r,c+1);
return size;
} // end getBlobSize()
public void mousePressed(MouseEvent evt) {
// The user has clicked the mouse on the applet. If the
// user has clicked on a position in the grid, count
// the number of squares in the blob at that position.
int row = (evt.getY() - 10) / SQUARE_SIZE;
int col = (evt.getX() - 10) / SQUARE_SIZE;
if (row < 0 || row >= rows || col < 0 || col >= columns) {
message.setText("Please click on a square!");
return;
}
for (int r = 0; r < rows; r++)
for (int c = 0; c < columns; c++)
visited[r][c] = false; // Clear visited array before counting.
int size = getBlobSize(row,col);
if (size == 0)
message.setText("There is no blob at (" + row + "," + col + ").");
else if (size == 1)
message.setText("The blob at (" + row + "," + col + ") contains 1 square.");
else
message.setText("The blob at (" + row + "," + col + ") contains " + size + " squares.");
repaint();
}
public void mouseReleased(MouseEvent e) { } // Methods required by MouseListener interface
public void mouseClicked(MouseEvent e) { }
public void mouseEntered(MouseEvent e) { }
public void mouseExited(MouseEvent e) { }
} // end class Blobs
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