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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.

Can I assign an image gradient to a rectangle

I'm currently making Mario as a school graphics project.
I have most of the collisions done, but I just want the land and bricks to actually look like land and bricks instead of just colored rectangles. I have an ImageIcon for the "land" in my graphics project. The problem is that it is only 16x16 pixels large. In order to make enough land by just making each part of the land one 16x16 pixel, it would essentially be horribly inefficient.
I was wondering if I could get the ImageIcon or possibly buffered image and use it as the "color" for a rectangle to make the chunks of land easier. If that's not possible, can you offer other suggestions on how to go about this problem?

Using a background of tiled images, a texture:
private BufferedImage image;
URL url = getClass().getResource("/mytexture.png");
assert url != null;
image = ImageIO.read(url);
#Override
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
Rectangle rect = new Rectangle(0, 0, width, height);
Rectangle textureRect = new Rectangle(0, 0, image.getWidth(), image.getHeight());
TexturePaint paint = new TexturePaint(image, textureRect);
g2.setPaint(paint);
g2.fill(rect);
}
In general create your own JPanel.
Gimp and other tools allow to create a tilable image by ensuring that a line running to a border will enter at the opposite border.

How to fade out the edges of a Java2D Area object?

I have a method that creates shadows based on where things are on the screen and the final product of that method is an Area, which I then draw onto the screen and it contains all shadows on screen in the same Area. This is because the drawn shadows are a low opacity so if it is not all one thing they will overlap and the opacity will make it look weird.
The issue that I want the shadows to look like they fade out, but I have absolutely no idea how, or if that would even be possible. Is there a way to soften the edges of the Area or make them gradient fade out? I tried to do graphics2D.setPaint(new GradientPaint[a gradient effect]) but it did nothing.
Thanks in advance
EDIT: Here is a screenshot of the program making a shadow around a 'building' rectangle. The green rectangle is to show the effect of the shadow. The end result I want is instead of the shadow abruptly ending, it should fade out.

i guess you have problems setting up the proper colors for the gradient:
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.GREEN);
g.fillRect(30, 30, 50, 20);
Graphics2D g2d = (Graphics2D) g;
Polygon p = new Polygon(new int[]{10,20,50,50,40,10}, new int[]{10,10,40,50,50,20}, 6);
Area a = new Area(p);
Color b = new Color(0xFF000000, true); //using colors with transparency!!!
Color w = new Color(0x00FFFFFF, true); //using colors with transparency!!!
//try to use proper values for the x/y values - both, start and end
GradientPaint gradient = new GradientPaint(0, 0, b, 40, 40, w);
g2d.setPaint(gradient);
g2d.fill(a); // fill your area!
}
result is a gradient with alpha (Transparency) ...
Area drawn in red <==> Area drawn with Gradient
don't forget to set the alpha value 0xAARRGGBB to FF for 100% opaque (0xFF000000 is black 100%opaque) to 0 (0x00FFFFFF white, 100% transparent)

Convert Jpanel to PNG image in java

How to remove Background of Jpanel while converting image (png). I tried following line to remove the background of the panel but The converted image background become black.
g2.clearRect(0, 0, getWidth(), getHeight());

draw a filled rectangle with the background color...
Color backGround = getBackGround();
g2.setColor(background);
g2.fillRect(0,0,getWidth(), getHeight() );

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);
}