Why did we have a new class file?

how can we use that smaller file?

Hey Aditya,

We can't actually use this ourselves, as to us it isn't a readable format. Java knows how to read it for us though, so we'd just call it with java Treet.

Note that this would actually throw an error as we're trying to run a class without a main() method. However, it's the same thing we're doing when we call java Example, we're telling Java to run the Example.class file rather than the Example.java file.

So, to summarize:

• When programming, we use the .java files, which are in a human-readable format.
• When running the program, we use the javac command to compile our human-readable code into a smaller, more efficient file, the .class file. This code is readable to the computer, not us, and provides binary instructions for how to operate.
• Finally, we use the java command to run the code that is readable to the computer - the .class files.

Hopefully this explains things but if you're not quite there, let me know :)

So we can delete that file? Is it just a binary form of the file that had been runned? If we run our program multiple times then wouldn't a lot of these files clutter in our folders and make everything look messy?

Hey again Aditya,

The file will overwrite itself whenever you run javac again, preventing the clutter you're on about :)

Also just to clarify, it's not a binary file of a program that has been run, it's a binary file of a program that has been compiled. Even if you were to just use the command javac without java (Compiling, not running), these files would still be created.

so if we delete them and then compile again, then they would be recreated? And if we compile again without deleting then the existing one would be rewritten?

Yep! You got it :)

k thanks!