OpenJDK

Browse source of Java 7 on Github: https://github.com/openjdk/jdk7-jdk/tree/master/src/share/classes/java/util

Browse source of Java 8 on OpenJDK Java.net mercurial repo: http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/ff6c76f7733e/src/share/classes/java/util/