All java classes and objects gone (eclipse, android SDK)

I've got t开发者_Python百科his really weird problem, have been working on a project all night and suddenly when I open Eclipse, I get hundreds of errors.

Nothing from String to Java.IO can be found... text like import java.io can not be resolved is everywhere. I have no clue what I have done, anyone can give me a hint? I would really appreciate it!

/Nick

ALSO, check if your JRE is selected as the Default JRE in the Eclipse-Preferences (under Java). Common cause for me at least.

Possible fixes:

-Reset the path to the Android SDK.

-Check if all libraries are on place

-Clear the project and try to rebuild

-Refresh the project

-Check the Console tab - sometimes the root of all problems is shown there.

-Check if there is some problems in the res dir, sometimes gen/R.java could't be build because of that

Happened to me after refactoring once. Check your .project file. Make sure it contains those entries:

<buildSpec>
            <buildCommand>
                    <name>org.eclipse.jdt.core.javabuilder</name>
                    <arguments>
                    </arguments>
            </buildCommand>
    </buildSpec>
    <natures>
            <nature>org.eclipse.jdt.core.javanature</nature>
    </natures>