Java |
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Java - Package
Creating , Import and Run
In this example, I have created four java files in c:\temp folder as shown below. For now, there are only java files in this folder and there is no sub folders in it. Pay attention to how the folder structure changes as we compile these java files.
c:\temp>dir
Volume in drive C has no label. Volume Serial Number is 568E-ECD3
Directory of c:\temp
01/06/2018 01:39 AM <DIR> . 01/06/2018 01:39 AM <DIR> .. 01/05/2018 10:53 PM 144 Hello.java 01/06/2018 01:33 AM 161 HelloWorld.java 01/06/2018 01:35 AM 389 PrintMessage.java 01/05/2018 10:53 PM 144 World.java
Contents of these files are as shown below.
Compile each of the files using -d option as shown below. With '-d .' , all the package folders are created as sub folders in current folder. c:\temp>javac -d . HelloWorld.java c:\temp>javac -d . Hello.java c:\temp>javac -d . World.java c:\temp>javac -d . PrintMessage.java
Now list all the files including the subfolder. You would notice that several server folders are created by compile process as commented below.
c:\temp>dir/s
Volume in drive C has no label. Volume Serial Number is 568E-ECD3
Directory of c:\temp
01/05/2018 10:53 PM 144 Hello.java 01/06/2018 01:33 AM 161 HelloWorld.java 01/06/2018 02:45 AM <DIR> MessageCollections 01/06/2018 01:35 AM 389 PrintMessage.java 01/05/2018 10:53 PM 144 World.java
Directory of c:\temp\MessageCollections <-- created by package MessageCollections;
01/06/2018 02:45 AM <DIR> . 01/06/2018 02:45 AM <DIR> .. 01/06/2018 02:45 AM <DIR> Hello 01/06/2018 02:43 AM <DIR> HelloWorld 01/06/2018 02:45 AM 515 PrintMessage.class 01/06/2018 02:45 AM <DIR> World 1 File(s) 515 bytes
Directory of c:\temp\MessageCollections\Hello <-- created by package MessageCollections.Hello;
01/06/2018 02:45 AM 416 Hello.class
Directory of c:\temp\MessageCollections\HelloWorld <-- created by package MessageCollections.HelloWorld;
01/06/2018 02:43 AM 438 HelloWorld.class
Directory of c:\temp\MessageCollections\World <-- created by package MessageCollections.World;
01/06/2018 02:45 AM 416 World.class
Now let's run a class. You can run the class with main() function as shown below. Note that I am running the class in the parent folder to the package folder.
c:\temp>java MessageCollections.PrintMessage
Hello, World Hello World
Just for your reference, I will show the result of running the program in different folder.
c:\temp\MessageCollections>java PrintMessage
Error: Could not find or load main class PrintMessage
c:\temp\MessageCollections>java MessageCollections.PrintMessage
Error: Could not find or load main class MessageCollections.PrintMessage
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