You will need at least JDK 1.1. The Java home page is at the Sun site. Sun also provides Documentation and tutorials. A version of this comes with the Core Java book on CD-ROM. You should also load the documentation, which can be viewed with any web browser.
Look at Java Developer Connection for information for Java developers. You may join for free.
If you prefer an integrated environment try:
CodeWarrior or Café or JBuilder. CodeWarrior is highly recommended and includes Java as well as C++ and Object Pascal.
J++ is strongly NOT recommended as it is not a complete implementation of Java. Visual Age is mildly NOT recommended as its code is difficult (impossible) to read. The JDK is the cheapest alternative (free) but is awkward to use initially.
If you use JDK you will need to set it up first. The integrated environments set themselves up when you install them.
If you use the JDK you need an editor to create Java files. Here is one that is free and integrated with the JDK. Dick Chase's Java Editor. You can also get (for $25) a version of Kawa (PC only) that is a nice project manger for Java.
Currently the best browser for Java is Netscape . Earlier versions do not support new features of Java. Explorer 4 may or may not support the features you need.