Java Reference
In-Depth Information
FIGURE 30-5
An instance of
Name
and its shallow clone
first
last
april
, an instance of
Name
"April"
"Jones"
twin
, the shallow clone
april.clone()
last
first
A shallow clone is good enough for the class
Name
. Recall that instances of
String
are immutable.
Having an instance of
Name
and its clone share the same strings is not a problem because no one can
change the strings. This is good news since, like many classes that Java provides,
String
has no method
clone
. Thus, if we change the clone's last name by writing
twin.setLast("Smith");
twin
's last name will be
Smith
, but
april
's will still be
Jones
, as Figure 30-6 shows. That is,
setLast
changes
twin
's data field
last
so that it references another string
Smith
. It does not
change
april
's
last
, so it still references
Jones
.
FIGURE 30-6
The clone
twin
, after the statement
twin.setLast(“Smith”)
changes one of its data fields
first
last
april
, an instance of
Name
"Jones"
"April"
"Smith"
twin
, the shallow clone
april.clone()
first
last
Programming Tip:
Shallow copies of data fields that reference immutable objects are
typically sufficient for a clone. Sharing an immutable object is usually safe.
