Software Engineering for Students A Programming Approach

204 Chapter 15 ■ Object-oriented programming
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}
public Alien(int newX, int newY, int newSize) {
x = newX;
y = newY;
size = newSize;
alienImage = new ImageIcon("c:/alien.jpg");
}
public void moveLeft(int amount) {
x = x - amount;
}
public void moveRight(int amount) {
x = x + amount;
}
public void display(JPanel panel) {
Graphics paper = panel.getGraphics();
alienImage.paintIcon(panel, paper, x, y);
}
public int xCoord {
get {
return x;
}
set {
x = value;
}
}
The header for a property looks similar to a method header, except that there are
no brackets to specify parameters. The property consists of two complementary components
– one has get as the heading and the other has set as the heading. The get
part is like a function method – it returns the desired value. The set part is like a
method – it assigns the value using the special keyword value as shown. Note that
this code is in the style of Java, but it is not Java, since Java does not support a property
mechanism.
If we only need a way of viewing a property (but not changing its value), we write
the property declaration like this:
public int xCoord {
get {
return x;
}
}
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