Javac not compiling, caching old file, maybe?

Question

Windows 7 x64

Bad problem description I know, but it's really hard to explain.

Basically I was trying to make some tweaks to an old program in IntelliJ after recently reformatting Windows and reinstalling java and all that jazz. No matter what I changed in the program, the output wasn't changing. Didn't matter what I commented out or changed.

So after a bit of frustration I decided to do some base testing to make sure I wasn't just losing my mind. I made an entirely new directory. And in that directory I made one file (using Sublime Text, not IntelliJ). Your classic "Hello World" program.

public class FrequencyCounter {
    public static void main(String args[]) {
        System.out.println("Hello World");
    }
}

That was the only file in the directory. Ran

javac FrequencyCounter.java

Seemed to compile fine, no errors, generated a FrequencyCounter.class file in the directory. Ran

java FrequencyCounter

And got this error:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
        at FrequencyCounter.main(FrequencyCounter.java:50)

Obviously this doesn't make any sense. It's like it's not running the FrequencyCounter class in that directory, but some older cached one somewhere else. Just for sanity's sake I copied the file, but changed it to HelloWorld.java and public class HelloWorld { ..... }, that compiles and runs fine (in the same directory).

If it helps:

D:\Copy\Code\Learning\CS\IntelliJ\test>java -version
java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

D:\Copy\Code\Learning\CS\IntelliJ\test>javac -version
javac 1.7.0_07

Answer 1

Assuming what you tell us is correct, it is running a FrequencyCounter class from somewhere else. The most likely thing is that your classpath is set to a directory or jar that already has a FrequencyCounter class in it, and it's running that.