Monday, March 16, 2015

Java API - Predefined Packages

Package NameExample ClassesFunctionality (Purpose)
java.langSystem, String, Object, Thread, Exception etc.These classes are indispensable for every Java program. For this reason, even if this package is not imported, JVM automatically imports.
java.utilThese are called as utility (service) classes and are used very frequently in coding.
java.ioFileInputStream, FileOutputStream, FileReader, FileWriter, RandomAccessFile, BufferedReader, BufferedWriter etc.These classes are used in all I/O operations including keyboard input.
java.netURL, ServerSocket, Socket, DatagramPacket, DatagramSocket etc.Useful for writing socket programming (LAN communication).
java.appletAppletContext, Applet, AudioStub, AudioClip etcRequired for developing applets that participate on client-side in Internet (Web) programming.
java.awtButton, Choice, TextField, Frame, List, Checkbox etc.Essential for developing GUI applications.
java.awt.eventMouseListener, ActionListener, ActionEvent, WindowAdapter etc.Without these classes, it is impossible to handle events generated by GUI components
java.sqlDriverManager, Statement, Connection, ResultSet etcRequired for database access in JDBC applications.

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