How can I run a single file while there are some bugs in the others in the same directory without opening a new project for this class?

Replace Before Launch steps with Build, no error check:

Note that javac compiler has certain errors limit, if there are more errors reported, your file may not compile at all, in this case you will need to switch to Eclipse compiler which is more tolerant to the number of errors or you can use Recompile context menu to build the valid file manually.