New to Java

 I am trying to draw a circle with centre at the end point of Line but the centre is not exactly at the the end point.
. . .
can some body please guide me what is the problem?

The Java API for 'drawOval' will tell you the problem - have you read it?

https://docs.oracle.com/javase/7/docs/api/java/awt/Graphics.html#drawOval(int,%20int,%20int,%20int)

Draws the outline of an oval. The result is a circle or ellipse that fits within the rectangle specified by the x, y, width, and height arguments. 
 The oval covers an area that is width + 1 pixels wide and height + 1 pixels tall.

You need to specify the coordinates of the 'bounding rectangle' and the circle will be drawn INSIDE it.

 int x1=30;int ix1;
 int y1=30;int iy1;
 int x2=60;int ix2;
 int y2=60;int iy2;
 public void paint(Graphics g) {
 g.drawLine(x1, y1,x2, y2);
 g.drawOval( x1, y1, 10, 10);
 g.drawOval( x2, y2, 10, 10);

So the TOP LEFT CORNER of your first 'bounding rectangle' is at x1, y1 and the height and width are 10.

You need to use x1 - 5 and y1 - 5.