FULL PRODUCT VERSION :
java version "1.7.0_40"
Java(TM) SE Runtime Environment (build 1.7.0_40-b43)
Java HotSpot(TM) 64-Bit Server VM (build 24.0-b56, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Windows 7 Ultimate 64 bit SP 1

A DESCRIPTION OF THE PROBLEM :
Take this code:

new Rectangle(0,0,20,20).outcode(new Point(20, 20));

The result is 0 which is invalid to my opinion. It seems 0 should be returned if the point is inside the rectangle but it is not since the lower right Point of this rectangle has 19 for it's x and y value. Rectangle.contains(point) confirms this.

The bug is caused by these two lines of code:
Rectangle line 1145: } else if (x > this.x + (double) this.width) {
Rectangle line 1152: } else if (y > this.y + (double) this.height) {

In both lines the > operator should be a >= to solve this problem. This same code is also used in the Rectangle2D.Double and Rectangle2D.Float subclasses of Rectangle2D. And After checking it's source code it seems JDK 8 has this problem too.

REGRESSION. Last worked in version 7u40

REGRESSION : Additional Information
java version "1.7.0_40"
Java(TM) SE Runtime Environment (build 1.7.0_40-b43)
Java HotSpot(TM) 64-Bit Server VM (build 24.0-b56, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Execute this code in a main and check the variable output.
int outcode = new Rectangle(0,0,20,20).outcode(new Point(20, 20));
boolean inside = new Rectangle(0,0,20,20).contains(new Point(20,20));


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
outcode = 12
The result of Rectangle2D.OUT_BOTTOM | Rectangle2D.OUT_RIGHT

Variable 'inside' is false
Since the point is not inside the rectangle
ACTUAL -
outcode = 0
This means there was no bitmask applicable and the point should be inside the rectangle.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public void testCase() {
   int outcode = new Rectangle(0,0,20,20).outcode(new Point(20, 20));
   boolean inside = new Rectangle(0,0,20,20).contains(new Point(20,20));
   System.out.println(String.format("Outcode is %d and inside is %s"
      , outcode, inside);
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
In my case I can decrease the width and height of the rectangle by 1 or move the point 1 position in both x and y direction to solve the problem.

But I am in the process of cleaning up some of the code and will probably let my custom classes extend Rectangle and Point. This will force me to create a new temporary rectangle or point and do the same trick in the code that gives the problem. Result is a small piece of workaround code. I can live with that.