Using Classes and Objects - Java Software Solutions: Foundations of Program Design - page 121

After printing the original phrase and its length, the concat method is executed
to create a new string object referenced by the variable mutation1:

mutation1

"Change is inevitable, except from vending machines."

Then the toUpperCase method is executed on the mutation1 object, and the
resulting string is stored in mutation2:

mutation2

"CHANGE IS INEVITABLE, EXCEPT FROM VENDING MACHINES"

Notice that the length and concat methods are executed on
the phrase object, but the toUpperCase method is executed on
the mutation1 object. Any method of the String class can be
executed on any String object, but for any given invocation, a
method is executed on a particular object. The results of execut-
ing toUpperCase on mutation1 would be very different from the results of
executing toUpperCase on phrase . Remember, each object has its own state,
which often affects the results of method calls.
Finally, the String object variables mutation3 and mutation4 are initialized by
the calls to mutation2.replace and mutation3.substring , respectively:

KEY CONCEPT
Usually a method is executed on a
particular object, which affects the
results.

mutation3

"CHANGX IS INXVITABLX, XXCXPT FROM VXNDING MACHINXS"

mutation4

"NGX IS INXVITABLX, XXCXPT F"

SELF-REVIEW QUESTIONS (see answers in Appendix N)
SR 3.6 Assume s1 , s2 , and s3 are String variables initialized to "Amanda" ,

"Bobby" , and "Chris" respectively. Which String variable or variables
are changed by each of the following statements?

a. System.out.println (s1);
b. s1 = s3.toLowerCase();
c. System.out.println (s2.replace('B', 'M'));
d. s3 = s2.concat(s1);

SR 3.7 What output is produced by the following code fragment?

String s1 = "Foundations";
String s2;
System.out.println (s1.charAt(1));
s2 = s1.substring(0, 5);
System.out.println (s2);