Thanks, you are all so nice; ./a.out worked.
Windows looks in local directory first.
Linux is unexpectedly different from windows.
It's tempting to say unexpectedly dumb,
but unix looked in local directory first 30 years ago,
so I suppose there is good reason to have changed it.
How do I deal with paths?
On a slightly more complicated program that uses imports,
I get the following when I compile and run:
gcj --main=LandsBug LandsBug.java
./a.out
Exception in thread "main" java.lang.UnsupportedOperationException
at java.awt.image.ColorModel.createCompatibleSampleModel(libgcj.so.70)
at java.awt.image.ColorModel.createCompatibleWritableRaster(libgcj.so.70)
at java.awt.image.BufferedImage.<init>(libgcj.so.70)
at LandsBug.main2(a.out)
at LandsBug.main(a.out)
And I can't figure out what to do.