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This article mainly introduces the relevant knowledge of what Java's method of writing HelloWorld is, the content is detailed and easy to understand, the operation is simple and fast, and it has a certain reference value, I believe you will have something to gain after reading this Java method of writing HelloWorld. Let's take a look at it.

System environment variable settings (jdk) in 1.Java development:

A man who wants to be good at his work is sharper than his tools. We have to go through the level of environment variables. Here are the environment settings in various operating systems.

In win2000/winxp:

Right-click my computer à attributes à advanced à environment variables

Classpath=.;jdk installation lib

Path=jdk installation directory bin

Note: it must not be ignored. He is referring to our current working directory. Without him, there would be a lot of trouble.

In winme:

"start à Program à attachment à system tools à system Information", select the tool à system configuration utility à environment

Settings:

Classpath=.;jdk installation lib

Path=jdk installation directory bin

In win98:

To modify autocexe.bat is to modify the automatic batch file.

Add:

Set classpath=.;jdk installation lib

Set path=jdk installation directory bin;%path%

In Linux:

Assuming that JDK is installed under / home/jdk1.4.0/, open / etc/profile and add:

PATH= "/ home/jdk1.4.0/bin:$PATH"

CLASSPATH=.:/home/jdk1.4.0/jre/lib/rt.jar:/home/jdk1.4.0/lib/tools.jar

JAVA_HOME=/home/jdk1.4.0

Export PATH CLASSPATH JAVA_HOME

2. After setting up our working environment, let's take a look at our HelloWorld program.

Public Class HelloWorld {

Public void HelloWorld () {

/ / Constructor

}

Public static void main (String args [])

{

System.out.println ("HelloWorld!")

}

}

There are three errors in the above program, see? Don't laugh, this kind of mistake will happen. Here is the code after correcting it:

Public class HelloWorld {

Public HelloWorld () {

/ / Constructor

}

Public static void main (String args [])

{

System.out.println ("HelloWorld!")

}

}

The case of class and System, although this problem generally does not appear, but the case problem is indeed a basic problem worthy of attention in the whole java world, so I will write it out to remind you, as long as you do not have to waste time and effort on such a mistake, you can think that I am just to make you laugh. Constructors are optional for HelloWorld, but I intend to add this constructor for two reasons: first, the constructor does not return a value, as we all know, even beginners will probably be very disdainful of this, why take it out. But it is true that many beginners will return a void,void is also a return value, this concept is my first purpose, some beginners will think that void just does not return value, wrong! Second, you should write a default constructor for your class, even if it does nothing but play the same role as the default constructor given to you by the system. When you don't write a default constructor, the system will give you one, but only if you don't have any constructors in your class. Ignoring this problem may cause problems with your inheritance system. Maybe it's too early to say this here, so it won't be said in the textbook, but it's always good to remember these things first so as not to cause a big stumble. (by the way, constructors can also be protected and private. It doesn't have to be public. Don't blame me for remembering ^ ^. Indeed, there are many people who think that the constructor must be public, wrong! ).

(3) there is no problem with the program and environmental variables, but there will still be problems:) Let's see what we should pay attention to in our implementation.

Compilation without packages:

Javac class name .java

Java class name

Compiling without packages should generally be fine as long as you pay attention to case.

Javac HelloWorld.java should not be written as javac helloworld.java

Java HelloWorld should not be written as java HelloWorld.class

In addition, generally speaking, at this time, everyone's working directory is the same as the directory where HelloWorld.java is located, which is the initial environment variable. " It's working.

Compilation with packages:

The parent directory class name of the javac-d package. Java

Java package name. Class name

It is important to note that everyone's working directory should be the same as the parent directory of the package.

There is another question. Let's take a look at the question first (although it has little to do with HelloWorld, but the problem is also very representative)

My bag is as follows:

Package c05

Public class PackagedClass {

Public PackagedClass () {

System.out.println ("Creating a packaged class")

}

Public static void main (String [] args) {}

}

The procedure is as follows:

/ / package c05

Import c05.PackagedClassboardAccording to / if it is changed to import c05.please, an error will be reported.

Public class Foreign {

Public static void main (String [] args) {

PackagedClass pc = new PackagedClass ()

}

}

This is the end of the article on "what is the way Java writes HelloWorld?" Thank you for reading! I believe that everyone has a certain understanding of the knowledge of "what is the method of Java writing HelloWorld". If you want to learn more knowledge, you are welcome to follow the industry information channel.

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