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Can a RadialGradientPaint have multiple center points?

I am currently trying to add a day/night cycle to my game, and I am having trouble with lighting. If there is a light source, I want it to create a circle of light around its area. I've made night time by drawing a black rectangle over the screen that becomes less transparent when its night time. That makes the whole screen darker. The code that I have works for one light source, but if I have a light source that overlaps another light source, it makes a strange darker ring. I understand what is causing that ring, but nothing I have tried is removing the ring.
public void render(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(new Color(20, 20, 20, transparency));
float[] dist = { 0.5f, 1.0f };
Color[] color = { new Color(230, 230, 180, 150), new Color(20, 20, 20, transparency) };
//Color[] color = { new Color(230, 230, 180, 150), new Color(0, 0, 0, 0) }; //Old unused color for the gradient
Area a = new Area(new Rectangle(0, 0, Main_Game.WIDTH, Main_Game.HEIGHT));
for (int i = 0; i < lightList.size(); i++) {
RadialGradientPaint p = new RadialGradientPaint(lightList.get(i).center, lightList.get(i).size, dist, color);
g2d.setPaint(p);
g2d.fillOval(lightList.get(i).center.x - lightList.get(i).size, lightList.get(i).center.y - lightList.get(i).size, lightList.get(i).size*2, lightList.get(i).size*2);
a.subtract(new Area(new Ellipse2D.Double(lightList.get(i).center.x - lightList.get(i).size, lightList.get(i).center.y - lightList.get(i).size, lightList.get(i).size*2, lightList.get(i).size*2)));
}
g2d.setColor(new Color(20, 20, 20, transparency));
g2d.fill(a);
}
That code has a linked list that holds all the light sources. And the transparency variable stores the transparency the box that darkens the screen when it's night time.
The ideal way to fix this would be to combine all the RadialGradientPaint objects for each light into one paint object and that way, the lights wouldn't overlap weirdly.
Here is what it looks like when it works with only one light source:
Here is a picture of the weirdness of lighting that I'm getting at night time (there is no issue during the daytime of the game) when there are two light sources close to each other:
Any sort of help or recommendation to setup this lighting would be greatly appreciated :)
I have tried subtracting one lighting circle from another so that they aren't overlapping, but that made the two lights not merge very nicely. I tried drawing the lights as a rectangle instead of an oval but that made a similar issue.

Java Swing Graphics2d rotation jumping

I'm writing a simple game for studying purposes. Everything goes fine except one little thing...
I cant figure out how to rotate square without this ugly jumping
here a simplified version of my program illustrating an issue, here i use one timer, but in original program i have 2 timers one for handle game state and second for repaint:
public class soQuestion extends JLabel {
double r;
#Override
public void paintComponent(Graphics g1) {
Graphics2D g = (Graphics2D) g1;
g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BICUBIC);
g.setRenderingHint(RenderingHints.KEY_RENDERING,
RenderingHints.VALUE_RENDER_QUALITY);
g.clearRect(0,0, getWidth(), getHeight());
g.translate(getWidth()/2, getHeight()/2);
g.rotate(r);
g.translate(-20, -20);
g.fillRect(0, 0, 40, 40);
}
public static void main(String[] args) {
JFrame frame = new JFrame();
soQuestion question = new soQuestion();
frame.add(question);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setSize(200, 200);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
new javax.swing.Timer(10, new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
r += 0.005;
question.repaint();
}
}).start();
}
}
jumping is more visible if rotation delta values is small, for fast rotated objects is less visible..
all rendering hints i used has no effect
PS: Sorry for my english
PPS: i can provide more details if needed, how it looks in full version:

Thanks for all participants!
It is fully my mistake and inattention. I was copied this code section from some source :
g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
And before ask a question here i couldn't saw that i used hint related to text rendering.
Special thanks to mr #Pshemo for suggesting of using this rendering hint:
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
I was know about it before asking, but i'm a human and could not figure out where a mistake for an a hour and asked.
PS: sorry for my english

I'm a new contributor, so if its not the best help, sry but i am trying :)
have you tried a solution where you are using Math.toRadiants() in your g.rotate() function? in this video: Java: Rotating and scaling images
the image rotates without jumping, it's at 6:42 in the video.
So in your solution, it would look like that: g.rotate(Math.toRadiants(r += 0.005));

Java Graphics2D Image Moving

So in this block of code, a 40x40 square can move across a window by calling directional methods, and I'm trying to get a spaceship to appear instead of the square. No matter what I try, it just isn't working.
public void paintComponent (Graphics g) {
ImageIcon wallpaper = new ImageIcon("images/JGalagawallpaper.png");
image = wallpaper.getImage();
g.drawImage(image, 400, 400, null);
ImageIcon ship = new ImageIcon("images/galaga.png");
galaga = ship.getImage();
super.paintComponent(g);
Graphics2D graphic = (Graphics2D) g;
graphic.fill(new Rectangle.Double(x, y, 40, 40));
//graphic.drawImage(galaga, x, y, 40, 40);
}
My question is, how do I get that thing to appear? I already tried tinkering with graphic.drawImage, however that didn't really work out as well as I hoped. That's what the commented out code is.

g.drawImage(image, 400, 400, null);
First you draw the image.
super.paintComponent(g);
Then you invoke the above code which is used to pint the background color of the panel, thus overwriting the image. The above statement should be the first statement of the painting method.
ImageIcon wallpaper = new ImageIcon("images/JGalagawallpaper.png");
A painting method is for painting only. Don't do I/O in the method. The image should be read in the constructor of your class so that it is only read once, not every time the component is repainted.
You also need to look at the coordinates of where you paint the image. Maybe the panel is not that big?
Did you verify that the image was read properly by display its size?

How to use a simple way to rotate a rectangle or triangle in java?

I'm currently working on a project with the theme of earth hour, and we are only allowed to use rectangles, circles and triangles. Here's the image i'm tring to create (not exactly, mine will be much more simplified!):
https://www.google.com/search?q=earth+hour&biw=1366&bih=586&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj__5H0vtvQAhXLrlQKHTi8BagQ_AUIBygC#imgrc=fQkBxn0a8LnwbM%3A
(not sure if you could see the link)
But when i'm coding it, i'm running into trouble to rotate those rectangles to stand on the tangent line of the circle. I'm a student just learnt some basics of java, like loops and arrays. So my quesiton is that if there's some understandable way that doesn't involve some complex and exotic methods that could rotate those rectangles? I know it will probably involve some complicated solutions that is beyond my knowledge. But any help is much appreciated.
this is part of the code that i build the building standing perpendicularly to the circle(earth):
// create mid buildings
Color blc = new Color(0, 0, 0);
Rectangle midBld = new Rectangle(240, 220, 20, 40, blc);
midBld.draw(g);
Rectangle midBld1 = new Rectangle(242, 190, 16, 30, blc);
midBld1.draw(g);
Triangle midBld2 = new Triangle(250, 160, 8, 30, blc);
midBld2.draw(g);
Triangle midBld3 = new Triangle(250, 160, -8, 30, blc);
midBld3.draw(g);

A Rectangle cannot be rotated, its edges are always in parallel to the axis. But you can rotate and translate the coordinate system in witch you draw the shapes. From Graphics2D API doc.
All coordinates passed to a Graphics2D object are specified in a device-independent coordinate system called User Space, which is used by applications. The Graphics2D object contains an AffineTransform object as part of its rendering state that defines how to convert coordinates from user space to device-dependent coordinates in Device Space.
Graphics2D also provide two methods that are useful in this task: translate that moves the origin of the coordinates and rotate that, well, rotates the system.
package graphics;
import javax.swing.*;
import java.awt.*;
/**
* Earth Hour
*/
public class RotateRect extends JFrame {
private static final int WIDTH = 400;
private static final int HEIGHT = 400;
public RotateRect() {
this.setSize(WIDTH, HEIGHT);
this.setTitle("Rotate Rectangles");
this.setContentPane(new JPanel() {
#Override
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
// Background: White
g2.setColor(Color.WHITE);
g2.fillRect(0, 0, this.getWidth(), this.getHeight());
// Draw "Earth": Center(200, 400), Radius=200
g2.setColor(Color.BLACK);
g2.fillOval(0, 200, 400, 400);
// Move origin to center of the canvas (surface of earth)
g2.translate(200, 200);
// Rotate the coordinate system, relative to the center of earth.
// note x, y are in the translated system
// Transforms are accumulative
g2.rotate(-Math.PI/6, 0, 200);
// Fill a rectangle with top-left corner at (-20, 80) in the rotated system
// It's important to make the rectangle symmetrical to the y-axis, otherwise the building looks
// funny.
// Also, make the building "sunk" a little, so that it's fully on the ground.
g2.fillRect(-20, -80, 40, 100);
g2.rotate(Math.PI/3, 0, 200);
g2.fillRect(-20, -80, 40, 100);
g2.rotate(-Math.PI/6, 0, 200);
g2.fill(new Rectangle(-20, -80, 40, 100));
}
});
}
public static void main(String [] args) {
RotateRect rr = new RotateRect();
rr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
EventQueue.invokeLater(()->rr.setVisible(true));
}
}

java graphics - a shape with two colours

(this is java) I have an oval, representing a unit. I want the colour of the oval to represent the unit's health. So a perfectly healthy unit will be all green. and with the unit's health decreasing the oval starts filling with red from the bottom. so, on 50% health the oval would be red in bottom half and green in the top half, and fully red when the unit's dead.
I'm sure the solution here must be obvious and trivial , but I just can't see it.
thanks a lot

You can draw a red oval in the background, then draw a green intersection of an oval and a rectangle, where the rectangle starts below the oval, then moves further to the top to reveal more of the red oval beneath.
You might like to read up on how to construct complex shapes out of primitives here

Override the paint method something like this:
public void paint(Graphics graphics)
{
super.paint(graphics);
Rectangle originalClipBounds = graphics.getClipBounds();
try
{
graphics.clipRect(100, 100, 100, 25);
graphics.setColor(Color.RED);
graphics.fillOval(100, 100, 100, 100);
}
finally
{
graphics.setClip(originalClipBounds);
}
try
{
graphics.clipRect(100, 125, 100, 75);
graphics.setColor(Color.BLUE);
graphics.fillOval(100, 100, 100, 100);
}
finally
{
graphics.setClip(originalClipBounds);
}
}
Might want to enhance it with some double buffering but you get the gist.

You can set the clip on the graphics when you draw the green. Only things within the clip actually get painted.
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D)g.create();
g2d.setColor(Color.RED);
g2d.fillOval(10, 10, 200, 100);
g2d.setColor(Color.GREEN);
g2d.setClip(10, 10, 200, 50);
g2d.fillOval(10, 10, 200, 100);
}