Mutable, Immutable, and Cloneable Objects - Data Structures and Abstractions with Java - page 791

Had we failed to clone the data field fullName —that is, had we omitted the statement
theCopy.fullName = (Name)fullName.clone();
the student's full name would be shared by the original instance and its clone. Figure 30-8
illustrates this situation.

FIGURE 30-8

An instance of Student and its clone, including a shallow copy
of fullName

first last

fullName fullName

"Lo"

"Kim"

"1234"

id

id

An instance of Student

The shallow clone

Question 4 Suppose that x is an instance of Student and y is its clone; that is,
Student y = (Student)x.clone();

a. If you change x 's last name by executing

Name xName = x.getName();
xName.setLast("Smith");
does y 's last name change? Explain.

b. If you fail to clone fullName within Student 's clone method, will changing x 's last name

change y 's last name as well? Explain.

Note: Within each public clone method, you typically perform the following tasks:

•

Invoke the clone method of the superclass by writing super.clone() .

•

Enclose this call to clone in a try block, and write a catch block to handle the possible
exception CloneNotSupportedException . You can skip this step if super.clone() invokes
a public clone method.

•

Clone the mutable data fields of the object that super.clone() returned, when possible.

•

Return the clone.

30.19

Example: Cloning a CollegeStudent object. Now let's add a clone method to a subclass of
Student . Segment C.8 of Appendix C defines such a subclass, namely the class CollegeStudent .
After we add an implements clause to its definition, the class has the following form:
public class CollegeStudent extends Student implements Cloneable
{

private int year; // year of graduation
private String degree; // degree sought