Java Notes

Java Notes: - one public class per file and the filename should be named after the public class name - The top level class cannot be private or protected - Multiple classes can be declared in a file but only one can be Public. If you ever are in a situation where you need to use two classes with the same name but in different packages, then using imports does not work. You will need to refer to each class by their fully qualified name in your source file. The following code compiles successfully: public class FullyQualifiedDemo { public javax.management.AttributeList a1; public javax.swing.text.html.parser.AttributeList a2; } Example: Take note of the command line arguments (dir structure) where it can compile and where it can run from Code: Message.java: package org.rakesh; public class Message { public void PrintMessage(String msg) { System.out.println(msg); } } TestMessage.java: package org.rakesh.test; import org.rakesh.Message; public class TestMessage { public static void main(String[] args) { Message m; m = new Message(); m.PrintMessage("Rakesh Prajapati"); } } NOTE: (no other dir path other than below could compile or run) To Compile: bash-4.1$ pwd /home/oracle/workspace/learning/src bash-4.1$ javac -d ../bin Message.java bash-4.1$ pwd /home/oracle/workspace/learning/src bash-4.1$ javac -cp ../bin -d ../bin TestMessage.java To Run: bash-4.1$ pwd /home/oracle/workspace/learning/bin bash-4.1$ java org/rakesh/test/TestMessage Rakesh Prajapati