The term “Java API” refers to the set of classes, interfaces, methods, and packages that are part of the Java programming language and its standard libraries. These APIs provide a wide range of functionality and tools for developing Java applications. Java APIs are organized into various packages, each addressing specific areas of functionality. Here are some of the core Java APIs and their key areas:

1. Java SE API (Standard Edition):

   • java.lang: Fundamental classes and exceptions, including Object, String, and Exception.
   • java.util: Data structures like ArrayList, HashMap, and date/time utilities.
   • java.io: Input and output operations, including file and stream handling.
   • java.net: Networking and URL handling.
   • java.math: Arbitrary-precision arithmetic (e.g., BigInteger, BigDecimal).
   • java.time: Date and time handling introduced in Java 8.
   • java.nio: Non-blocking I/O and file system operations.
   • java.security: Security-related classes and cryptography.
   • java.awt and javax.swing: GUI (Graphical User Interface) components and windowing systems.

2. Java EE API (Enterprise Edition):

   • javax.servlet: Servlet API for building web applications.
   • javax.ejb: Enterprise JavaBeans for building enterprise applications.
   • javax.jms: Java Message Service for messaging between distributed components.
   • javax.ws.rs: Java API for RESTful Web Services.
   • javax.persistence: Java Persistence API for database access (part of JPA).
   • javax.transaction: API for managing transactions in enterprise applications.

3. Java FX API:

   • javafx.scene: JavaFX GUI components for building rich desktop applications.

4. Java ME API (Micro Edition):

   • Designed for developing applications for resource-constrained devices like mobile phones and embedded systems.

5. Java API for XML Processing (JAXP):

   • APIs for XML parsing and manipulation, including DOM and SAX parsers.

6. Java API for JSON Processing (JSON-P):

   • APIs for parsing and generating JSON data.

7. Java Naming and Directory Interface (JNDI):

   • API for accessing naming and directory services, often used in enterprise applications for resource lookup.

8. Java Management Extensions (JMX):

   • API for managing and monitoring Java applications.

9. Java 2D API:

   • Graphics and 2D rendering capabilities.

10. Java Sound API:

    • Audio processing and playback.

11. Java Cryptography Extension (JCE):

    • Cryptographic algorithms and services.

12. JavaMail API:

    • Sending and receiving email messages.

13. JavaBeans Activation Framework (JAF):

    • Handling data stored in various MIME types.

14. Java Authentication and Authorization Service (JAAS):

    • Authentication and authorization for Java applications.