JAVAFX BASICS - Introduction to Java Programming: Comprehensive Version - page 576

106 Circle circle = new Circle(centerX, centerY, clockRadius);
107 circle.setFill(Color.WHITE);
108 circle.setStroke(Color.BLACK);
109 Text t1 = new Text(centerX - 5 , centerY - clockRadius + 12 , " 12 " );
110 Text t2 = new Text(centerX - clockRadius + 3 , centerY + 5 , "9" );
111 Text t3 = new Text(centerX + clockRadius - 10 , centerY + 3 , "3" );
112 Text t4 = new Text(centerX - 3 , centerY + clockRadius - 3 , "6" );
113
114 // Draw second hand
115 double sLength = clockRadius * 0.8 ;
116 double secondX = centerX + sLength *
117 Math.sin(second * ( 2 * Math.PI / 60 ));
118 double secondY = centerY - sLength *
119 Math.cos(second * ( 2 * Math.PI / 60 ));
120 Line sLine = new Line(centerX, centerY, secondX, secondY);
121 sLine.setStroke(Color.RED);
122
123 // Draw minute hand
124 double mLength = clockRadius * 0.65 ;
125 double xMinute = centerX + mLength *
126 Math.sin(minute * ( 2 * Math.PI / 60 ));
127 double minuteY = centerY - mLength *
128 Math.cos(minute * ( 2 * Math.PI / 60 ));
129 Line mLine = new Line(centerX, centerY, xMinute, minuteY);
130 mLine.setStroke(Color.BLUE);
131
132 // Draw hour hand
133 double hLength = clockRadius * 0.5 ;
134 double hourX = centerX + hLength *
135 Math.sin((hour % 12 + minute / 60.0 ) * ( 2 * Math.PI / 12 ));
136 double hourY = centerY - hLength *
137 Math.cos((hour % 12 + minute / 60.0 ) * ( 2 * Math.PI / 12 ));
138 Line hLine = new Line(centerX, centerY, hourX, hourY);
139 hLine.setStroke(Color.GREEN);
140
141 getChildren().clear();
142 getChildren().addAll(circle, t1, t2, t3, t4, sLine, mLine, hLine);
143 }
144 }

create a circle

create texts

create second hand

create minute hand

create hour hand

clear pane
add to pane

The program displays a clock for the current time using the no-arg constructor (lines
18-20) and displays a clock for the specified hour, minute, and second using the other
constructor (lines 23-28). The current hour, minute, and second is obtained by using
the GregorianCalendar class (lines 86-96). The GregorianCalendar class in the
Java API enables you to create a Calendar instance for the current time using its no-
arg constructor. You can then use its methods get(Calendar.HOUR) , get(Calendar
.MINUTE) , and get(Calendar.SECOND) to return the hour, minute, and second from a
Calendar object.
The class defines the properties hour , minute , and second to store the time represented
in the clock (lines 10-12) and uses the w and h properties to represent the width and height of
the clock pane (line 15). The initial values of w and h are set to 250. The w and h values can be
reset using the setW and setH methods (lines 69, 80). These values are used to draw a clock
in the pane in the paintClock() method.
The paintClock() method paints the clock (lines 99-143). The clock radius is propor-
tional to the width and height of the pane (line 101). A circle for the clock is created at the center
of the pane (line 106). The text for showing the hours 12, 3, 6, 9 are created in lines 109-112.