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# Concentric circle using JPanel

Dj Lee
Greenhorn
Posts: 3
Hello, I'm a beginner in Java and I'm trying to create a jpanel that
creates 10 concentric circles with random radius. But I'm having a bit trouble with it.

Here are my codes:

When I run this, I get only one circle (sometimes none...)
if i set radius = generator.nextInt(MAX_DIAMETER) + 1;

But if i replace MAX_DIAMETER which is 600, to something small maybe 100.
than i get 5-10 circles...

What am i doing wrong??

Paul Clapham
Sheriff
Posts: 22472
43
Sounds to me like using a big number causes most of the 10 circles to be located outside of the box displayed in your panel.

Dj Lee
Greenhorn
Posts: 3
Paul Clapham wrote:Sounds to me like using a big number causes most of the 10 circles to be located outside of the box displayed in your panel.

the panel is running in (600, 600) so isnt it suppose to show all the circles since I set the diameter of the circle to not exceed 600?

Paul Clapham
Sheriff
Posts: 22472
43
That would be true if the centres of the circles were all at (0, 0). But it isn't true if the centre of the circles is way outside your box.

Debashis jain
Greenhorn
Posts: 3
When I run this, I get only one circle (sometimes none...)
if i set radius = generator.nextInt(MAX_DIAMETER) + 1;

But if i replace MAX_DIAMETER which is 600, to something small maybe 100.
than i get 5-10 circles...

What am i doing wrong??

The radius of the circle is (diameter/2)
"generator.nextInt(MAX_DIAMETER) "when you are using this function that's mean you are expecting a random number from 0-600
so when you write the code diameter=2*radius....actually the diameter at most of the time becomes as big as 1200,and your panel size is (600,600) so it won't suit the created circles.

Campbell Ritchie
Marshal
Posts: 55678
161
I think this thread would sit better on our GUIs forum: moving.

Campbell Ritchie
Marshal
Posts: 55678
161
. . . and welcome to the Ranch

 Don't get me started about those stupid light bulbs.