Java in Linux
The examples have been separated into two major sections: Without Package and With Package. If your Java code
uses packages, go to section 2.
1. Without Package
Suppose you have these two files which should be in the same directory:
HelloWorld.java which contains:
public class HelloWorld
{
public static void main(String[] args)
{
Dumb dumb = new Dumb();
System.out.println("Hello World");
// use doit to print the message for each argument
for (int i = 0; i < args.length; i++)
{
dumb.doit(args[i]);
}
System.exit(0);
}
}
Dumb.Java which contains:
public class Dumb
{
String locString;
public Dumb()
{
locString = "";
}
public void doit(String str)
{
System.out.println("Hello " + str);
}
}
1.1 How to Compile ClassName.java producing ClassName.class?
$ javac ClassName.java
1.2 How to Run the program?
$ java MainClassName programCommandLineArguments
• The MainClassName must be the name of the class that has the main method.
• programCommandLineArguments are the command line arguments to the main method.
1.3 Example putting it all together
1. Compile each Java file producing ClassNa me.class files.
$ javac HelloWorld.java
$ javac Dumb.java
2. Execute the class containing the main passing command line arguments
$ java HelloWorld Fred Wilma
Generated Output from that program:
Hello World
Hello Fred
Hello Wilma
2. With Package
Suppose your code is part of a package named "hello". Your code should be placed in the hello directory:
HelloWorld.java which contains:
package hello;
public class HelloWorld
{
public static void main(String[] args)
{
Dumb dumb = new Dumb();
System.out.println("Hello World");
// use doit to print the message for each argument
for (int i = 0; i < args.length; i++)
{
dumb.doit(args[i]);
}
System.exit(0);
}
}
Dumb.Java which contains:
package hello;
public class Dumb
{
String locString;
public Dumb()
{
locString = "";
}
public void doit(String str)
{
System.out.println("Hello " + str);
}
}
2.1 How to Compile ClassName.java producing ClassName.class?
You can compile the code from within the hello directory:
$ javac ClassName.java
Alternatively, you can compile the code from the directory above the hello directory:
$ javac hello/ClassName.java
In both cases, a successful compile will create ClassName.class in the hello directory.
1.2 How to Run the program?
You should run the code from the directory above the hello directory:
$ java packageName.MainClassName programCommandLineArguments
• packageName is the name of the package for that MainClassName and it is also the name of the directory
containing its MainClassName.class file.
• The MainClassName must be the name of the class that has the main method.
• programCommandLineArguments are the command line arguments to the main method.
1.3 Example putting it all together
This example assumes the .java files are in the hello directory. The current directory is the one above hello.
1. Compile each Java file producing ClassNa me.class files.
$ javac hello/HelloWorld.java
$ javac hello/Dumb.java
2. Execute the class containing the main passing command line arguments
$ java hello.HelloWorld Fred Wilma
Generated Output from that program:
Hello World
Hello Fred
Hello Wilma