Common packages for Java

java.lang: this package contains the core classes of the Java language, such as String, Math, Sytem, Thread, etc. You do not need to use import statement import to use this package, and the system will automatically import all the classes in this package.

java.util: this package contains a large number of java utility classes/interfaces and collection framework classes/interfaces. Such as Arrays, List, Set, etc.

java.net: this package contains some of the Java network programming related classes/interfaces.

java.io: this contains some input/output programming classes/interfaces for Java.

java.text: this package contains some Java formatting-related classes.

java.sql: this package contains java's classes/interfaces for JDBC database programming.

java.awt: this package contains the classes/interfaces associated with the abstract window toolset (Abstract Window Toolkits), which are used to build graphical user interface (GUI) programs.

java.swing: this package contains classes/interfaces for Swing GUI programming that can be used to build platform-independent GUI programs.