Re: cloning

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <>
Mon, 16 Jan 2012 15:29:53 -0500
On 1/16/2012 1:27 PM, albert kao wrote:

I want to clone the following class so is the following code ok?
public class TestImpl implements Serializable {

     private int id = 0;
     private java.sql.Timestamp createDateTime;
     private java.sql.Date expiryDate;
     private java.math.BigDecimal amount;
     private java.sql.Timestamp deleteTimestamp;

     // other methods
     // ...

     public Object clone() throws CloneNotSupportedException {
         return (TestImpl)super.clone();

By convention, the returned object should be obtained by calling
super.clone. If a class and all of its superclasses (except Object) obey
this convention, it will be the case that x.clone().getClass() ==

By convention, the object returned by this method should be independent
of this object (which is being cloned). To achieve this independence, it
may be necessary to modify one or more fields of the object returned by
super.clone before returning it. Typically, this means copying any
mutable objects that comprise the internal "deep structure" of the
object being cloned and replacing the references to these objects with
references to the copies. If a class contains only primitive fields or
references to immutable objects, then it is usually the case that no
fields in the object returned by super.clone need to be modified.

The method clone for class Object performs a specific cloning operation.
First, if the class of this object does not implement the interface
Cloneable, then a CloneNotSupportedException is thrown. Note that all
arrays are considered to implement the interface Cloneable. Otherwise,
this method creates a new instance of the class of this object and
initializes all its fields with exactly the contents of the
corresponding fields of this object, as if by assignment; the contents
of the fields are not themselves cloned. Thus, this method performs a
"shallow copy" of this object, not a "deep copy" operation.

The class Object does not itself implement the interface Cloneable, so
calling the clone method on an object whose class is Object will result
in throwing an exception at run time.

Note what it says about mutable objects.


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