Common Java Packages

java.lang.*
provides a basic class for programming using the Java programming language. The most important class is Object (which is the root of the class hierarchy) and class (its instance represents a class in the running application).
java.util.*
contains the collection framework, legacy collection classes, event models, date and time facilities, internationalization, and various utility classes (string tag generator, random number generator and bit array, date dates class, Stacks stack class, Vector vectors class, etc.). Collection class, Time processing mode, date and time tools and other common tool kits
java.io.*
Java's core library, Java.io, provides a comprehensive IO interface. Include: file read and write, logo device output. Io in Java is input and output on a stream basis, and all data is serialized to the output stream or read in from the input stream.
java.net.*
Not all systems support the IPV6 protocol, and when the Java network connection stack tries to detect it and use it transparently when it is available, you can also disable it with System properties. In cases where IPv6 is not available or is explicitly disabled, inet6address is no longer a valid parameter for most network connection operations. While you can guarantee that methods such as Java.net.InetAddress.getByName do not return inet6address when you look for hostnames, you can still create such objects by passing literal values. In this case, most methods will throw an exception when using the Inet6address call.
java.sql.*
provides an API to access and process data stored in a data source (typically a relational database) using the JAVATM programming language. This API includes a framework that allows you to dynamically install different drivers to access different data sources

java.awt.*

The package contains support for graphical user interface (GUI) classes

javax.swing.*

The package holds classes that support Swinggui components and is more flexible than java.awt-related components

Common Java Packages