In Eclipse you want to navigate to the source code of standard class String, and you get the following message: Source not found

Solution

(1) Install JDK in your laptop, and then configure it into Windows->Preferences->Java->Installed JRE. Delete existing entry for JRE:

And click Add… button:

Add JDK instead:

Once added, set JDK as default entry:

(2) Preferences->Java Build Path, remove existing entry of JRE:

Click Add Library button:

Choose JDK instead:

Once done, you can now navigate to the source code of standard class like String now.