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set through a parameter to the constructor and the field is immutable. Provide an accessor
method for it called isCourseText .
Exercise 2.92 Challenge exercise Create a new project, heater-exercise , within BlueJ. Edit
the details in the project description—the text note you see in the diagram. Create a class,
Heater , that contains a single field, temperature whose type is double-precision floating
point —see Appendix B, section B.1, for the Java type name that corresponds to this descrip-
tion. Define a constructor that takes no parameters. The temperature field should be set
to the value 15.0 in the constructor. Define the mutators warmer and cooler , whose effect
is to increase or decrease the value of temperature by 5.0° respectively. Define an accessor
method to return the value of temperature .
Exercise 2.93 Challenge exercise Modify your Heater class to define three new double-
precision floating point fields: min , max , and increment . The values of min and max should
be set by parameters passed to the constructor. The value of increment should be set to
5.0 in the constructor. Modify the definitions of warmer and cooler so that they use the
value of increment rather than an explicit value of 5.0. Before proceeding further with this
exercise, check that everything works as before.
Now modify the warmer method so that it will not allow the temperature to be set to a value
greater than max . Similarly modify cooler so that it will not allow temperature to be set to
a value less than min . Check that the class works properly. Now add a method, setIncre-
ment , that takes a single parameter of the appropriate type and uses it to set the value of in-
crement . Once again, test that the class works as you would expect it to by creating some
Heater objects within BlueJ. Do things still work as expected if a negative value is passed to
the setIncrement method? Add a check to this method to prevent a negative value from
being assigned to increment .
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