Source code for the Java library classes

Here's the browsable source code for OpenJDK 7.

Update: As of June 2018 grepcode seems to be down. Here you can find an alternative.

Update^2: As of October 2020, the two previous links do not work. View it at OpenJDK and vote up the answer by Nosrep, which I got it from.

For old versions of Java with separate JRE and JDK downloads, download the JDK. The sources for the public classes are in src.zip.