new data type: named constant

a named constant is assigned a value that can not change during the running of the program

syntax used to declare a named constant: final datatype CONSTANTNAME $=$ value;

for example: final double PI $=3\mathrm{.}14159$;

in math, pi is known as a constant used to compute the area of a circle

go to page $43$ of your textbook and read the program under Listing $2\mathrm{.}4$

predict how the program would run and what output would appear in the output window

open a new NetBeans project, using the same name as the book $($ComputeAreaWithConstant$)$

copy the code into your program $($including the comments$)$

run the program; when the program asks for the radius, enter a number in the output window

then: add a command line on the line below your declaration of PI

PI $=3$;

what do you think will happen when you run the program?

run it and see what happened $($look in the output window$)$

you should see an error message because you can't reassign a value to a constant

delete the error$-$causing line of code