java - Can't debug anything in eclipse "Source not found" -

i can't debug since yesterday , don't know is. programs run fine, , there no error whatsoever. doesn't matter program debug, can make hello world-program , debugger wont start. get:

source not found, confirm perspective switch

if click yes; debugger info

if click no, nothing happens.

i've tried configuring debugger adding projects "source", doesn't it. :/ i've searched web more solutions nothing works me.

if don't have source jar code you're trying step into, can't see code, because it's executable version.

meaning, example, if you're trying debug code in json.jar file, should have json-source.jar can attach file can step , see what's happening. if can elaborate more on situation, might able more.