Detailed description: 

       "Now we'd like to do some compilation. I have a file that is the source code for the bank account, and it's called BankAccount.java.  To compile this code, we use the javac command.  Let me show you this on the command line.  I'm currently several levels deep in directories, and if you look at the screen, you'll see that we have BankAccount.java there. 
       To execute the compiler, we type in javac BankAccount.java.  We have to 
specify the suffix.  And also remember that the upper and lower case convention must be followed and that it must match the internal class name.  So we couldn't type in bankaccount.java.  The file name must match the class name. 
       Next the compiler, the Java compiler, says it's compiling BankAccount.java.  And if you look at the results,  we now have a .class file in our directory in addition to the .java file, which is the byte code that's been representing the bank account class.  So now we have a bank account .class file as a result.  What we need to do now is to run the program and get the results."