I am developing an android application using Eclipse IDE. Eclipse is showing error icon on the android application, but I can't find any error anywhere inside the sub folders(sections). Because of this error, I can't run or debug the application. When I try to run or debug, "Your project contains error(s), please fix them before running your application" error window is appearing.

Why can't I find any error inside my android application ? How can I fix this issue ?

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UPDATE :

I found a problem. The R.java file is now missing. How this happened ?