Netbeans Download Javadoc repeatedly
It seems strange that you download the Javadoc everytime... To configure javadoc in Netbeans :
Tools -> Java Platforms
Choose your JDK, the in the pane Javadoc the URL should be :
http://download.oracle.com/javase/7/docs/api/
If you have problem with this remove it and download the javadoc zip and add it instead of the url.
JDK8 updated link (thanks @Tim S) : http://www.oracle.com/technetwork/java/javase/documentation/jdk8-doc-downloads-2133158.html
JDK 14 updated link: https://www.oracle.com/java/technologies/javase-jdk14-doc-downloads.html
I am using JDK 1.8 with Netbeans 8.0.2.
I was also facing the same problem as Netbeans was continuously downloading the Javadoc from internet.
I found solution to this as:
Open Netbeans, then go to Tools -> Java Platforms. Then go to Javadoc tab and remove any URLs added for platform javadoc.
In Source tab you can add specific Javadoc from your local environment, that you can download from oracle website i.e. Java SE 8 Doc.
This stopped continues download of Javadoc from internet.