The document discusses the Java 2 Platform, Mobile Edition (J2ME) Wireless Messaging API (WMA), which allows applications to send and receive short text and binary messages. It describes how to check if the WMA API is available, the key interfaces and classes in the WMA package, and provides examples of how to send and receive both text and binary messages synchronously and asynchronously.

4. WMA 1.0 Package All WMA-specific interfaces and classes are contained in a single package, javax.wireless.messaging, which defines all the APIs required for sending and receiving wireless text, binary Subinterface of the GCF Connection, which provides a factory of Messages, and methods to send and receive Messages MessageConnection Subinterface of Message that provides methods to set and get the text payload TextMessage Defines the listener interface to implement asynchronous notification of Message objects MessageListener Subinterface of Message that provides methods to set and get the binary payload BinaryMessage Base Message interface, from which subinterfaces (such as TextMessage and BinaryMessage) are derived Message Description Interfaces

7. Message Connection and Its Relationship to GCF