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# Thread: PointCoordinates

- 05-08-2014, 11:25 AM #1Member
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## PointCoordinates

What are the x- and y-coordinates of the Points referred to as p1, p2, and p3 after the following code executes? Give your answer as an x-y pair such as (0, 0). (Recall that Points and other objects use reference semantics.

PHP Code:Point p1 = new Point(); p1.x = 17; p1.y = 9; Point p2 = new Point(); p2.x = 4; p2.y = -1; Point p3 = p2; p1.translate(3, 1); p2.x = 50; p3.translate(-4, 5);

P1:

P2:

P3:

My guesses were: P1:(20,10) //Correct

P2:(50,-1) //Incorrect

P3:(0,4) //Incorrect

- 05-08-2014, 11:45 AM #2
## Re: PointCoordinates

The tricky part is at line 7: p3 points (no pun intended) to the same Point in memory as p2. The change you make to p3 will be performed on the same instance as p2. So, p2 and p3 always return the same values since they point to the same object.

*"It's not fixed until you stop calling the problem weird and you understand what was wrong." - gimbal2™ © 2013*

- 05-08-2014, 02:02 PM #3Member
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## Re: PointCoordinates

But what would the values turn out to be ?

p2.x = 50; that should change the value of p2.x=4 into p2.x=50 i presume, but its still a wrong answer.

- 05-08-2014, 02:46 PM #4

- 05-08-2014, 04:14 PM #5Moderator
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## Re: PointCoordinates

p1, p2 and p3 are references to Point objects.

They are not the objects themselves.

p1 refers to a Point that was created on this line:

Java Code:Point p1 = new Point();

Java Code:Point p2 = new Point();

p3 is declared as referring to p2, on this line:

Java Code:Point p3 = p2;

Please do not ask for code as refusal often offends.

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