Software Engineering for Students A Programming Approach

without difficulty. For example:
JButton button = new JButton("go");
16.3 Using packages 225
If the import statement was omitted, we could still use the class JButton, but we
would need to refer to it by its full name – javax.swing.JButton. This would be
inconvenient and cumbersome. Hence we see the value of the import statement.
If we only need to import an individual class, say JButton, from within a package,
we can spell it out:
import javax.swing.JButton;
Using * means that we want to import all the classes within the named package. So
if we need to use more than one from a package, it is simpler to use the * notation.
SELF-TEST QUESTION
16.1 Classes called Monday, Tuesday, Wednesday, Thursday, Friday,
Saturday and Sunday are grouped in a package called week. Write
down the Java import statement that will be needed to use the class
Friday. Write the statement to create an object friday of the class
Friday. Write down the import statement that will be needed to use all
the classes in the package.
In C and C++, a program almost always begins with an include declaration. For a
system package the declaration is typically:
#include
or, for a programmer’s own package:
#include "myFile.h"
The include statement is a directive to the compiler to include within the current
source file a copy of the named file. A file with the suffix .h is, by convention,
a header file and it is files of this type that normally appear in the include statement.
A header file is a source code file that contains the declaration of the methods
to be found within a package. These declarations are, in C terminology, the prototypes
of the available methods – their names and parameters. The C and C++ languages
have a rule that a method has to be declared (textually) before it can be used.
When a declaration like this is present, the program can refer to the methods within
the package described and it will compile successfully. Subsequently the object
code of the packages is linked.