as I understood, the method clone()
gives us the ability to copy object (no refernce) in Java. But I also read, that the copy is shallow. So what the point? Which a
The difference is that you can modify the cloned object without modifying the original object.
Point p = new Point(1,2);
Point p2 = p.clone();
Point p3 = p;
p2.x = 5;
p3.y = 7;
The change on p3
does feed back to p
, while the change on p2
does not.
Let's see how the situation is after the individual statements (assuming 1
, 2
, 5
, 7
would be objects):
Point p = new Point(1,2);
.-----. .-----.
p -----> | x -+--> | 1 |
| | '-----'
| | .-----.
| y -+--> | 2 |
'-----' '-----'
Point p2 = p.clone();
.-----. .-----. .-----.
p -----> | x -+--> | 1 | <--+- x | <----- p2
| | '-----' | |
| | .-----. | |
| y -+--> | 2 | <--+- y |
'-----' '-----' '-----'
Point p3 = p;
.-----. .-----. .-----.
p -----> | x -+--> | 1 | <--+- x | <----- p2
| | '-----' | |
| | .-----. | |
p3 -----> | y -+--> | 2 | <--+- y |
'-----' '-----' '-----'
p2.x = 5;
.-----. .-----. .-----. .-----.
p -----> | x -+--> | 1 | | x -+--> | 5 |
| | '-----' | | '-----'
| | .-----. | |
p3 -----> | y -+--> | 2 | <--+- y | <----- p2
'-----' '-----' '-----'
p3.y = 7;
.-----. .-----. .-----. .-----.
p -----> | x -+--> | 1 | | x -+--> | 5 |
| | '-----' | | '-----'
| | .-----. | |
p3 -----> | y | | 2 | <--+- y | <----- p2
'--+--' '-----' '-----'
| .-----.
'---> | 7 |
'-----'