My IDE is Netbeans. My professor asks me to submit the homework in both source code (.java files) and byte code. But I don't know how to convert my source code to byte code. I searched it on google but didn't find the answer. Please help. Thank you.
"Byte code" is what .class-files contain. The javac program takes source files as input and produces bytecode files.
If you have a source file homework/Main.java you would produce the corresponding bytecode file by running javac homework/Main.java. This would then produce a file homework/Main.class.
For more information, see https://docs.oracle.com/javase/7/docs/technotes/tools/#basic.