Java™ How To Program (Early Objects), Tenth Edition

Class EmployeeTest

EmployeeTest method main (Fig. 8.13) instantiates two Employee objects (lines 13–14). When each Employee object’s constructor is invoked, lines 15–16 of Fig. 8.12 assign the Employee’s first name and last name to instance variables firstName and lastName. These two statements do not make copies of the original String arguments. Actually, String objects in Java are immutable—they cannot be modified after they’re created. Therefore, it’s safe to have many references to one String object. This is not normally the case for objects of most other classes in Java. If String objects are immutable, you might wonder why we’re able to use operators + and += to concatenate String objects. String-concatenation actually results in a