Can't work on my java projects in Eclipse Juno

Question

I used to work in Eclipse Luna and had many projects in my workspace. Then I decided to start coding for Android and downloaded the ADT bundle from here . I imported my Luna workspace and it worked fine. However, whenever I open a class I get cannot be resolved errors everywhere on what used to be flawless code. What difference in packages is causing this? Why can't I write and compile Java in Juno?

Note that I don't see the errors in the package explorer on the left:

Answer 1

Your jdk is missing or incorrect. Check in ur build path of the project. Your jre is probably still referencing the old location.

Answer 2

You should create a new workspace and import your project folder by folder, omitting the folders generated by eclipse for the workspace to function properly.

for todo this: file>import>android>android exsisting proyect

Answer 3

select your project -> properties(Alt+Enter) ->Java Build Path -> Order and Export-> make sure android 4.1.1 or your target os Checkbok is selected.

if not then select click okay clean and rebuild the project. hope you will get your solution.