Defining Classes - Beginning Java - page 231

Note how you use the static toString( ) method defined in the Double class to convert the x value to a
String . The compiler inserts a call to the same method automatically for the y value, as the left operand
of the + operation is a String object. Note that you could equally well have used the valueOf() method
in the String class. In this case the statement would be written like this:
return String.valueOf(x) + ", " + y; // As "x, y"

TRY IT OUT: The Line Class
You can use Point objects in the definition of the class Line :

class Line {
Point start; // Start point of line

Point end; // End point of line

// Create a line from two points
Line(final Point start, final Point end) {
this.start = new Point(start);
this.end = new Point(end);

}

// Create a line from two coordinate pairs
Line(double xStart, double yStart, double xEnd, double yEnd) {
start = new Point(xStart, yStart); // Create the start point

end = new Point(xEnd, yEnd); // Create the end point

}

// Calculate the length of a line
double length() {
return start.distance(end); // Use the method from the

Point class
}

// Convert a line to a string
public String toString() {
return "(" + start+ "):(" + end + ")"; // As "(start):(end)"

} // that is, "(x1,

y1):(x2, y2)"

Directory "Try Geometry"

You should save this as the file Line.java in the Try Geometry directory.