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Java Graphics 2d avoid Polyline distorted corners

i'm working on a graphic interface for drawing subway maps. A line is represented with station as circles and a polyline to link them.You can move the stations with a mouseDrag and of course it updates the displaying map in real time. My problem is when stations comes to a certain angle, there is a polyline distortion and the corner created by the 2 lines is out of the station circle display, i'd like to know if there is a way to avoid this.
screenshots of the app with the polyline issue
here's my code for the polyline's draw
//x and y point array creation
xPoints = new int[this.stationViews.size()];
yPoints = new int[this.stationViews.size()];
for (int i=0;i<this.stationViews.size();i++) {
//fill arrays with the center point of circles representing stations
xPoints[i] = this.stationViews.get(i).getStation().getPosX()-this.stationViews.size()/2;
yPoints[i] = this.stationViews.get(i).getStation().getPosY()-this.stationViews.size();
}
//setting color
g2D.setColor(this.line.getColor());
//set stroke width relative to the zoom level
int strokeWidth=5;
if(!this.stationViews.isEmpty()) {
if (this.stationViews.get(0).getStationSize()>14) {
strokeWidth = this.stationViews.get(0).getStationSize()-13;
}else {
strokeWidth = 3;
}
}
g2D.setStroke(new BasicStroke(strokeWidth));
//draw the polyline
if (this.stationViews.size() >1) {
g2D.drawPolyline(xPoints, yPoints, this.stationViews.size());
}
//draw the station (g2D.drawCircle)
for (StationView stationView : stationViews) {
stationView.affiche(g2D,this.line.getColor());
}
thank you for your help

That is called the miter. You seem to be per default using JOIN_MITER, sharp joining of extended lines at the end, which can point far out of the join for small angles.
g2d.setStroke(new BasicStroke(strokeWidth,
BasicStroke.CAP_SQUARE, BasicStroke.JOIN_ROUND, 5));
miter a surface forming the beveled end or edge of a piece where a joint is made by cutting two pieces at an angle and fitting them together.
It is also a bishop's cap with a pointy top, hence the name.

Points not filling trying to draw an arrow head (triangle) with Graphics2D

When trying to draw an arrowhead using Java Graphics2D by using points and inputting the coordinates.
g2.drawLine(xLeft+290, yTop + 80, xLeft+290,yTop + 100); //first arrow
Polygon arrowHead = new Polygon();
arrowHead.addPoint(xLeft+290, yTop+140);//firstpoint
arrowHead.addPoint(xLeft+285, yTop+120);//secondpoint
arrowHead.addPoint(xLeft+295, yTop+120);//thirdpoint
g2.fillPolygon(arrowHead);
This is my code for drawing the line and the arrowhead, I'm not sure at all of the coordinates are correct but I can't see the shape if it will not appear.

Set background color in java Graphics object

Good day,
Know that in Java Graphics object, we can user the setColor() method to set the object color. But this is only apply to the object border. Is it anyway to set color for the whole object? I means the background of the Graphics object.
void draw(Graphics g)
{
g.setColor(color);
g.drawRect(left, right, width, height);
}
Kindly advise.

use fillRect() method .
g.fillRect(left, right, width, height);
from javadoc
drawRect()
Draws the outline of the specified rectangle. The left and right edges of the rectangle are at x and x + width. The top and bottom edges are at y and y + height. The rectangle is drawn using the graphics context's current color.
fillRect()
Fills the specified rectangle. The left and right edges of the rectangle are at x and x + width - 1. The top and bottom edges are at y and y + height - 1. The resulting rectangle covers an area width pixels wide by height pixels tall. The rectangle is filled using the graphics context's current
color.
" this is only apply to the object border " because drawRect draw the outlines only.
" Is it anyway to set color for the whole object? " well you misunderstand . and setColor() set the color to what you draw if you draw a outline then you can see outline only and it's not because of setColor() set colors to border .

Getting translated coordinates from Android canvas

I am passing in an object for Android to paint using it's canvas. The object to rotated to match the horizon. I am trying to find the translated points which canvas calculates given the point and angle I give it.
For example:
I use the following canvas methods to paint it. Where x,y are the screen coordinates and rotation is the rotation of the screen relative to the horizon.
canvas.save();
canvas.translate(x,y);
canvas.rotate(rotation);
obj.paint(canvas);
canvas.restore();
obj.paint() looks like this (but you probably don't need to know it):
canvas.save();
canvas.translate(-width/2, -height/2);
setFill(true);
setColor(backgroundColor);
paintRect(canvas, x, y, width, height);
setFill(false);
setColor(borderColor);
paintRect(canvas, x, y, width, height);
canvas.restore();
paintRect() looks like this:
canvas.drawRect(x, y, x + width, y + height, paint);
What I am trying to figure out is; what are the corner points of the rectangle (green in this picture) after it has been rotated.
Here is an image of the result which is what I expect.

Rotating a Rectangle on an Image using Swing

Ok when a user draws a Rectangle on top of an image, I want to find all the rotated Rectangles ahead of time for all image rotation angles (90,180,270,360).
According to Java API I can just keep calling the Graphics2D rotate() method. I can then use this Graphics2D transformer to get the rotated Rectangle.
This works for the very first rotation(1.5708) call. I get the correct Rectangle Point. All other calls after that return the wrong Rectangle Point after using Transformer.
I think my problem is the Graphics2D translate(x,y). I don't understand how to use it.
Anyone knows how to fix my code so that it will return the correct Rectangle after every rotation?
Thank you.
public void rotateRectangles(BufferedImage bim,int width,int height,Rectangle rect){
BufferedImage bim = new BufferedImage(height, width,BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = (Graphics2D) (bufferedImage.createGraphics());
g2d.translate(bufferedImage.getHeight(),0);
//Get Rectangle for 90 degree image rotation. This always good.
g2d.rotate(1.5708);
Shape shape = g2d.getTransform().createTransformedShape(rect);
Rectangle rotatedRect = shape.getBounds();
System.out.println("rotated rectangle at 90 degrees. Point x="+rotatedRect.x+" y="+rotatedRect.y);
//Get Rectangle for 180 degree image rotation. Getting wrong rotatedRect.
g2d.rotate(1.5708);
shape = g2d.getTransform().createTransformedShape(rect);
rotatedRect = shape.getBounds();
System.out.println("rotated rectangle at 180 degrees. Point x="+rotatedRect.x+" y="+rotatedRect.y);
//Get Rectangle for 270 degree image rotation. Getting wrong rotatedRect.
g2d.rotate(1.5708);
shape = g2d.getTransform().createTransformedShape(rect);
rotatedRect = shape.getBounds();
System.out.println("rotated rectangle at 270 degrees. Point x="+rotatedRect.x+" y="+rotatedRect.y);
//Get Rectangle for 360 degree image rotation.Getting wrong rotatedRect.
g2d.rotate(1.5708);
shape = g2d.getTransform().createTransformedShape(rect);
rotatedRect = shape.getBounds();
System.out.println("rotated rectangle at 360 degrees. Point x="+rotatedRect.x+" y="+rotatedRect.y);
}
Thank you.

Instead of rotating the graphics context's affine transform via g2d.rotate(), consider using createTransformedShape() as suggested in this example.
Addendum: Note in particular that the baseline of the example Polygon is initially centered on the origin. As a result, the initial transformation is rotation around the origin. In your case, you can use the rotate() method that includes an anchor point, which would be the center of your rectangle.