How to attach javadoc for jar in eclipse?

For to add the Document to the Library, do the following things.

Project(Right Click)->Properties->Build Path -> libraries ->JRE System Library then expand each api and Added the location of API.

Now select the Library for which you want to add the Documents.

Click on Edit, then Navigate browser to select the Directory of the Documentation directory. Please try with only Directory, not the index.html file.

Right-click on the jar, click "Properties", then fill the javadoc location.