Writing the first Java program

public class hello{    //is the starting point of the program, and all programs start running public    static void Main (String args[])    {        System.out.println ( "Hello world!");}    }

Save the above code as a Hello.java file and enter [Javac Hello.java] on the command line (the JDK is installed and the installation path is added to the environment variable). If there is no error, then enter [Java Hello].

Command line output result: Hello world!

Note that if you declare a class as public, you also take the file name sing Woo the same name as the class. In other words, in a Java file, there can be at most one public class, otherwise. java files cannot be named.

In all Java application, all programs run from public static void main (String args[]).

The compilation and operation of Java code is as follows:

Writing the first Java program