Declarations. A declaration statement associates a variable name with a type at compile
time. Java requires us to use declarations to specify the names and types of variables.
By doing so, we are being explicit about any computation that we are specifying.
Java is said to be a strongly typed language, because the Java compiler checks for
consistency (for example, it does not permit us to multiply a boolean and a double).
Declarations can appear anywhere before a variable is first used—most often, we put
them at the point of first use. The scope of a variable is the part of the program where it
is defined. Generally the scope of a variable is composed of the statements that follow
the declaration in the same block as the declaration.