在jshell中使用C选项有什么用

Question

I have gone through the introduction to jshell guide and couldn't find description/examples about the -C option in jshell.

$jshell --help
 -C<flag>              Pass <flag> to the compiler.
                        Use one -C for each compiler flag or flag argument

Answer 1

You can use this option to make use of javac command line arguments for example consider this piece of code:

String str = (String)"Hello"

Starting jshell normally and using the same would result as:

---

While at the same time you can enable compiler errors on warning( -Werror ) and make use of the -Xlint key cast while compiling to warn you of the explicit cast used in the above code using -

jshell -C-Xlint:cast -C-Werror

and the same statement would result into warnings and error from Jshell compiler as:-

---

Though IMO, this certainly is documented far less in terms of what all flags shall/shall not be used while using the JShell -C command line option.

Answer 2

To pass options to the javac compiler that jshell is going to run to compile the statements in your REPL. One simple example (to see which classes are loaded), jshell -C-verbose . See also Standard Options for javac and Extra Options for javac for additional options you might specify.