LISTS, STACKS, QUEUES, AND PRIORITY QUEUES - Introduction to Java Programming: Comprehensive Version - page 780

84 animation.pause();
85 }
86
87 public void increaseSpeed() {
88 animation.setRate(animation.getRate() + 0.1 );
89 }
90
91 public void decreaseSpeed() {
92 animation.setRate(
93 animation.getRate() > 0 ? animation.getRate() - 0.1 : 0 );
94 }
95
96

public DoubleProperty rateProperty() {

97 return animation.rateProperty();

98 }
99
100 protected void moveBall() {
101 for (Node node: this .getChildren()) {
102 Ball ball = (Ball)node;
103 // Check boundaries
104 if (ball.getCenterX() < ball.getRadius() ||
105 ball.getCenterX() > getWidth() - ball.getRadius()) {
106 ball.dx *= -1 ; // Change ball move direction
107 }
108 if (ball.getCenterY() < ball.getRadius() ||
109 ball.getCenterY() > getHeight() - ball.getRadius()) {
110 ball.dy *= -1 ; // Change ball move direction
111 }
112
113

move all balls

change x direction

change y direction

// Adjust ball position

114 ball.setCenterX(ball.dx + ball.getCenterX()); adjust ball positions

115 ball.setCenterY(ball.dy + ball.getCenterY());

116 }
117 }
118 }
119
120 class Ball extends Circle {

121 private double dx = 1 , dy = 1 ;

declare d x and d y

122
123 Ball( double x, double y, double radius, Color color) {
124 super (x, y, radius);
125 setFill(color); // Set ball color
126 }
127 }
128 }

create a ball

The add() method creates a new ball with a random color and adds it to the pane (line
70). The pane stores all the balls in a list. The subtract() method removes the last ball in
the list (line 75).
When the user clicks the

+ button, a new ball is added to the pane (line 31). When the user

clicks the button, the last ball in the array list is removed (line 32).

The moveBall() method in the MultipleBallPane class gets every ball in the pane's
list and adjusts the balls' positions (lines 114-115).

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20.23

✓ ✓

What is the return value from invoking pane.getChildre() for a pane?

Check

Point