Java Packages,Java Package's Interview Questions ,core java IT technical interview questions

Java interfaces and classes are grouped into packages. The following are the java packages, from which you can access interfaces and classes, and then fields, constructors, and methods.


java.lang
Package that contains essential Java classes, including numerics, strings, objects, compiler, runtime, security, and threads. This is the only package that is automatically imported into every Java program.
java.io
Package that provides classes to manage input and output streams to read data from and write data to files, strings, and other sources.
java.util
Package that contains miscellaneous utility classes, including generic data structures, bit sets, time, date, string manipulation, random number generation, system properties, notification, and enumeration of data structures.
java.net
Package that provides classes for network support, including URLs, TCP sockets, UDP sockets, IP addresses, and a binary-to-text converter.
java.awt
Package that provides an integrated set of classes to manage user interface components such as windows, dialog boxes, buttons, checkboxes, lists, menus, scrollbars, and text fields. (AWT = Abstract Window Toolkit)
java.awt.image
Package that provides classes for managing image data, including color models, cropping, color filtering, setting pixel values, and grabbing snapshots.
java.awt.peer
Package that connects AWT components to their platform-specific implementations (such as Motif widgets or Microsoft Windows controls).
java.applet
Package that enables the creation of applets through the Applet class. It also provides several interfaces that connect an applet to its document and to resources for playing audio.

Java Interface where to Use,Core Java Tutorials

You use an interface to define a protocol of behavior that can be implemented by any class anywhere in the class hierarchy. Interfaces are useful for the following:
Capturing similarities between unrelated classes without artificially forcing a class relationship
Declaring methods that one or more classes are expected to implement
Revealing an object's programming interface without revealing its class. (Objects such as these are called anonymous objects and can be useful when shipping a package of classes to other developers.)