Sams Teach Yourself C in 21 Days

Java Language Fundamentals 705

BD4

You can also use the *wildcard to import all classes in a package:

import java.io.*;

This line imports all classes in the java.iopackage. Packages that are part of Java have

names starting with java. If your program makes reference to a class without having

imported it, the compiler generates an error. A Java program can have as many import

statement as it needs.

A package is simply a file that contains classes. Using the wildcard character,

Note you can include all of the classes from the file.

Methods ........................................................................................................

In Java, a methodis essentially the same thing as a function in C or C++. Methods are so

named simply because Java is a completely object-oriented language and, by convention,

objects have methods, not functions. You saw an example of a method in the Hello,

Worldexample presented on Bonus Day 1, “Object-Oriented Programming Languages.”

In a Java program, most of the code is in methods.

Comments ......................................................................................................

No programming language is complete without the capability to add comments to the

source code. Java has three comment styles. One is just like a C comment; anything

between/*and*/is a comment and is ignored by the compiler:

/* This is

all

one

big

comment */

The second style is the same as C++; anything after //on a line is a comment:

// This is a comment.

X = 5; //This is also a comment.

Java’s third comment style is used for automatic generation of documentation. It is like

the C comment style with the addition of an extra asterisk:

/** This comment will be included in class documentation

created by the Javadoc tool. */

With this style of comment, you can us a program called Javadoc to generate documenta-

tion from your program. The use of Javadoc is beyond the scope of this book, but you

need to know about this comment style in case you run across it in Java code.

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