JDK 1.4 Features

http://java.sun.com/j2se/1.4.2/docs/relnotes/features.html

Summary of New Features and Enhancements

Important day to day programming features 1

Logging API
Assertions
Preferences
Chained Exceptions
Collections
Regular Expressions

Next set of Important features

JDBC 3.0
Java Web Start
Endorsed Standards Override