Java 6 Illuminated: An Active Learning Approach, 2nd Edition

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Specifying a return value

for a constructor will cause

a compiler error in the

client program when the

client attempts to instanti-

ate an object of that class.

COMMON ERROR

TRAP

382 CHAPTER 7 Object-Oriented Programming,Part 2: User-Defined Classes

classes in more depth. It is also good practice to provide another construc-

tor that accepts values for all the instance variables.

On line 17, we instantiate an Auto object with an invalid argument for gallons

of gas. As Figure 7.1 shows, the constructor prints an error message. The object

is still created, but the value of its gallonsOfGas instance variable is 0.0.

Beware of this common error: declaring a ...