JavaTM ME classes can be divided into two parts: those inherited as a subset of the Java SE APIs and those that are new and specific to Java ME. This means that only a limited number of classes from the Java SE is supported and that there are classes included that are only available for Java ME. For more information on package release information, see section Java API release information.
User Interface package (javax.microedition.lcdui)
The MIDP User interface (UI) has a low-level API and a high-level API.
The low-level API is based on the use of the abstract class Canvas.
The high-level API classes Alert, Form, List,
and TextBox are extensions of the abstract class Screen.
The low-level API’s Canvas class allows applications
to have more direct control of the UI. It allows greater control of what is
drawn on the display, and receiving low-level keyboard events.
The high-level API classes are designed to provide abstractions and components that are highly portable across different mobile devices, as the actual implementation takes care of aspects such as drawing, font characteristics, navigation, scrolling, etc.
Application Life Cycle package (javax.microedition.midlet)
The Application Life Cycle package, also known as the MIDlet Package, defines MIDP applications and how they interact with the environment in which they run.
Networking package (javax.microedition.io)
MIDP 2.0 applications are able to communicate over a range of connectivity standards. MIDP 2.0 has support for HTTP and secure HTTP (HTTPS). It also encourages, but does not require, support for User Datagram Protocol (UDP), Transmission Control Protocol (TCP), and serial port communication.
Public Key package (javax.microedition.pki)
The Public Key package allows using certificates for authenticating information in secure connections.
Persistence package (javax.microedition.rms)
MIDP does not allow applications to read or write to a file system. However, Record Management System (RMS) can be used to store persistent data such as high-score tables and saved games.
MIDlets are allowed to create multiple record stores, as long as they have different names, and MIDlets can access record stores relating to other MIDlets within the same suite. Also, if explicit permission is given, MIDlets within other suites can also access the record store (a new feature in MIDP 2.0). For more information MIDlet suites, see section MIDlet suites.
Note: Using FileConnection API (JSR-75) allows accessing a file system.