When in Eclipse click ctrl + клик on the system class, for example, on String , a message appears that the source is not found on the path C:\Program Files\Java\jre7\lib\rt.jar
I went to Window / Preferences / Java / Installed JREs and added and selected JDK - D:\Program Files\Java\jdk1.7.0_10
But the source is still not located. Where else do you need to make changes?