Deep Copying Attempt

Question

I am trying to build a method to deep copy a class:

public MyClass clne() {
    MyClass cpy = new MyClass();
    cpy.var1 = getVar1(); //getVar1 is a method returning the value of var1
    cpy.var2 = getVar2();
    return cpy;
}

However, when I run:

MyClass x = new MyClass();
x.var1 = 18;
MyClass y = x.clne();
y.myMethod(); // Where myMethod is a method changing the value of var1 to, say 4.
System.out.println(x.var1);

The value of x.var1 is 4.

Am I doing something wrong? Thank you :)

What are the types of `var1` and `var2`? Are they `int`? `Integer`? — rgettman, Mar 22 '13 at 00:01
Even if it was `Integer`, surely it wouldn't matter since `Integer` is immutable? — Patashu, Mar 22 '13 at 00:02
They are int, but I tried with other mutable types (ie: string, float etc) and it gave the same error — Dario, Mar 22 '13 at 00:03
Can you show the entire declarations of the `var1` and `var2` variables in `MyClass`? — rgettman, Mar 22 '13 at 00:08
Can you post a [Short, Self-Contained, Correct Example](http://sscce.org/)? — ruakh, Mar 22 '13 at 00:09

score 0 · Answer 1 · answered Mar 22 '13 at 00:02

0

You should be creating a new instance of var1 rather than pointing to the old reference, unless they are primitives of course.

cpy.var1 = new Var1( getVar1() );

this will require you to write a copy constructor for whatever class Var1 is. This can be done in other ways though.

Hope that helps.

PS, you are basically doing a shallow copy.

answered Mar 22 '13 at 00:02

Adrian

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2
10

The OP says that they are primitives, not objects – Patashu Mar 22 '13 at 00:04
Is it new Var1 or new var1? (If it makes a difference) – Dario Mar 22 '13 at 00:04
Depends on the type of var1. as you assign it using x.var1 = 4, i assume it must either be an int or Integer, which means that what you wrote should be fine unless they are static members – Adrian Mar 22 '13 at 00:28

Deep Copying Attempt

1 Answers1