• Related classes can be grouped together in a package. Together the classes of a package form a way of programming in a particular area: together they define what is called an application programming interface (an API).
• Java has a large number of APIs already defined. Examples include APIs:
  • for file I/O,
  • for doing 2D and 3D graphics,
  • communicating with databases (JDBC),
  • for sending an e-mail message,
  • for enabling access to WWW pages,
  • for accessing objects of Java programs running on other computers,
  • for supporting the writing of applets.
• Some of these APIs are considered to be crucial, called the Core APIs.
• There are WWW pages documenting the Core APIs: http://java.sun.com/j2se/1.4.2/docs/api. These WWW pages can also be downloaded to filespace on your own computer.
• This Guide uses the notation javaapi:java/lang/String.html to refer to the WWW page http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html.