For visa from Japan

To apply for tourist L type in Japan, first, you need to provide a filled-out application form affixed with a passport-style photo, your passport and its photocopy, residence permit in there, round trip air tickets and hotel reservation. Next, submit the application to the CVASC.

When I come to China I will live in my friends house so I don’t book hotel so what should i write it in the application? And could i send the application by email or must to send it by post office? Thanks so much for your answer it’s useful!

If you don't have hotel reservation, you can ask your friend to send you an invitation letter. You should go there in person to submit the application or find someone else to do that on your behalf.