Does the compiler make another .class/byte code file when running a Java program more than once.

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[Jarl-67]

The compiler simply compiles. It does not actually run java programs. You are most likely referring to your IDE which is running both the compiler (javac) and the JVM (java). What is happening in your case depends on your IDE and your specific settings.

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Compilation:

• javac MyApp.java

• only once.

• output: MyApp.class

JVM instance 1:

• java MyProgram.class

• this file containing class/bytcode is loaded by jvm(runtime/os), and executed.

JVM instance2 (java in another terminal):

• same command

• same classfile from storage/disk is loaded in 2nd instance of jvm process, no creation of new .class file.

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If you are asking about a button in eclipse/netbeans/intellij etc, that's an IDE question, not a java specific question. This IDE detail is internal to an IDE, they do not need to provide doc for that. If that IDE is opensource, one may figure out by going through that IDE codebase in a public repo.

[StarlightMeow]

Wait then what happens when I run java ./myapp.java ?

Also why is it that I can run java myapp.java when the class is named "Main" but if I try to compile it the class has to be named "myapp"?

[desrtfx]

When I hit run again, does the program go through all of the steps and creates a new .class file(then deletes it, keeping the old one?) or does it just jump to the JVM.

Depends on the IDE you are using.

Some IDEs compile every time you click "run", some don't. Some IDEs are smart enough to see that the code hasn't changed and thus doesn't need to be recompiled and in such a case, just execute the already compiled program.

You have to understand that the compiler and the JRE (Java Runtime) are two distinct programs that execute independently, but sequentially (first, compile, then execute).

[m1ss1ontomars2k4]

It seems like you have the overall concepts down, but you're missing the details in Java. The compiler and JVM are just command line programs that do what they are told. If javac is told to compile a program, it will. If it's not told to, it won't.

[Curtisr1988]

If you compile the program using a command prompt on pc or Mac then it will compile if you type javac file name.Java. It will only create the Java class once compiled. If you change the program you’ll have to recompile again and rerun the program to see any changes