OK. Here is the exact things I did. All the txt is in the attached codes.zip
I was playing around with python -m http.server --cgi and decided to make a java cgi.
So 
1. I created one and compile it. (hellojava.java)
2. Test run it in console. (c1.txt)
3. as java class file cannot be directly executed, so I create a little batch file to run it. (runjava.bat)
4. and tested it in console (c3.txt)
5. start up the http.server --cgi (c2.txt)
6. then I fire up my firefox 35.0 and go to URL http://127.0.0.1:8000/cgi-bin/runjava.bat?hellojava
7. and got the expected result (r1.txt)
8. and the console of the http.server show expected result (cr1.txt)
9. then I try to pass parameter into the java cgi itself, so I go to URL http://127.0.0.1:8000/cgi-bin/runjava.bat?hellojava+test
10. results in an blank page, actual response is also blank.
11. console shows error message (cr2.txt)
12. so I run the generated command in actual console and get the same error (cr3.txt, I am using Chinese locale so I put the actual error and English on line 3)
13. and if I replace the '+' with ' ' in the command it will work as expected. (cr4.txt)