Unable to get javac to automatically recompile a source file

Question

I am experimenting with the javac command line options, in order to learn about the -sourcepath and -classpath options. When I run javac, having tried four different command line options for it, I am unable to obtain a recompiled .class file.

Here is my folder structure. Please note that due to testing, the Test.java file is located inside the "bat" folder, which is an admittedly odd location.

projects \ prj1 \ bat \ bat.bat
                        Test.java
                        Test.class   <--- unable to obtain recompiled file.

                  src \ Main.java
                        Main.class

The contents of my two .java test files are:

// Main.java, located in the src folder
class Main {
    public static void main(String[] args) {
        new Test();
    }
}

// Test.java, located in the bat folder
class Test {}

Regarding the execution of javac at the command prompt, here are four options that I have tried. I've run these commands from a batch file called bat.bat, which is located inside the "bat" folder.

javac ..\src\Main.java                      (no sourcepath, no cp)
javac -sourcepath . ..\src\Main.java        (sourcepath)
javac -cp . ..\src\Main.java                (cp)
javac -sourcepath . -cp . ..\src\Main.java  (sourcepath, cp)

In all of these javac commands above, I am unable to obtain a recompiled .class file, for the Test.java file. Is this because I have not edited the Test.java file, since initially compiling it? Please note that I have no CLASSPATH environment variable set. Thanks.

Answer 1

If class files are already present in the destination / output folder, javac will only recompile the source java file if it has been modified since the date/time of the class file.

If you want to recompile the source files, then first delete the *.class files before calling javac.