This section provides a tutorial example on how to place one Java class in an unnamed package and how to compile and run the class in an unnamed package.
I will begin with a simple case, where there is only one class that has no
package declaration statement, so it can be stored in any unnamed package.
Assuming that we have Hello.java entered
in a directory called C:\hy\src, enter the following commands in a command window:
C:\hy\src>type Hello.java
class Hello {
public static void main(String[] a) {
System.out.println("Hello world!");
}
}
C:\hy\src>del Hello.class
Could Not Find C:\herong\src\Hello.class
C:\hy\src>set CLASSPATH=
C:\hy\src>\jdk1.3.1\bin\java -version
java version "1.3.1_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.1_01)
Java HotSpot(TM) Client VM (build 1.3.1_01, mixed mode)
C:\hy\src>\jdk1.3.1\bin\javac Hello.java
C:\hy\src>\jdk1.3.1\bin\java Hello
Hello world!
C:\hy\src>del Hello.class
C:\hy\src>\jdk1.3.1\bin\javac -classpath \hy Hello.java
C:\hy\src>\jdk1.3.1\bin\java -classpath \hy Hello
Exception in thread "main" java.lang.NoClassDefFoundError: Hello
C:\hy\src>del Hello.class
C:\hy\src>\jdk1.3.1\bin\javac -classpath . Hello.java
C:\hy\src>\jdk1.3.1\bin\java -classpath . Hello
Hello world!
C:\hy\src>del Hello.class
This test tells us that:
I am using JDK 1.3.1_01.
If there is no -classpath command option specified, and no CLASSPATH environment
variable defined, there is one default class path: current directory.
Class paths are searched for the class being invoked in the execution process.
In the next test, let's move the current directory to a directory different than
the Hello.java directory, and run the following commands:
