Java Packages Overview

Java Packages overview

2020-10

Select from among the following, classes which are stored in the java.sql package.

  1. Connection
  2. Writer
  3. Reader
  4. FileWriter
  5. ResultSet

Answer: (a) Connection and (e) ResultSet

The java.sql package is the foundation for Java Database Connectivity (JDBC) and contains classes and interfaces for interacting with databases.

  • (a) Connection is an interface in the java.sql package used to establish a connection with a database.
  • (e) ResultSet is an interface in the java.sql package used to hold data retrieved from a database after executing an SQL query.
  • (b) Writer, (c) Reader, and (d) FileWriter are part of the java.io package, which is used for input and output operations, specifically character streams for the first two and file writing for the last two. They are not related to database connectivity.

Java Packages — Quick Reference

A compact, beginner-friendly list of common Java packages with their meanings and utilities.

1. java.lang

Meaning

Core language classes automatically imported in every Java program.

Utilities

Fundamental classes such as String, Object, System, Math, and Thread. Used for basic language operations, exceptions, and threading.

2. java.util

Meaning

General-purpose utility classes and data structures.

Utilities

Collections like ArrayList, HashMap, HashSet, LinkedList; helpers like Random, Scanner, and Collections. Also older date/time types such as Date and Calendar.

3. java.io

Meaning

Blocking input/output (I/O) operations using streams and readers/writers.

Core Stream Classes:

  • InputStream and OutputStream: Abstract base classes for reading and writing byte streams, respectively.
  • Reader and Writer: Abstract base classes for reading and writing character streams, respectively.

Utilities

File and stream classes such as FileReader, BufferedReader, FileWriter, InputStream, and OutputStream. Commonly used for reading/writing files and binary/text streams.

4. java.nio & java.nio.file

Meaning

New I/O — modern, often more efficient I/O APIs (introduced in Java 1.4 and enhanced in Java 7).

Utilities

Buffers, channels, non-blocking I/O, and convenient file utilities such as Files and Paths. Preferred for high-performance or async I/O and filesystem operations.

5. java.net

Meaning

Networking and communication APIs.

Utilities

Classes like Socket, ServerSocket, URL, and URLConnection for TCP/UDP sockets and working with URLs.

6. java.awt

Meaning

Abstract Window Toolkit — basic desktop GUI and drawing primitives.

Utilities

Low-level GUI components, events, layout managers, and 2D drawing. Often used as the foundation for older GUI toolkits.

7. javax.swing

Meaning

Rich GUI toolkit built on top of AWT.

Utilities

Components such as JFrame, JButton, JPanel, and JTable. Used to build desktop applications with richer UIs than AWT alone.

8. java.applet (obsolete)

Meaning

API for applets that used to run inside web browsers (now deprecated/removed).

Utilities

Was used to create small browser-based Java programs; not used in modern Java development.

9. java.sql

Meaning

APIs for interacting with relational databases via JDBC.

Utilities

Core JDBC interfaces and classes such as Connection, Statement, PreparedStatement, and ResultSet for database CRUD operations.

10. javax.sql

Meaning

Extensions to JDBC for enterprise features.

Utilities

Connection pooling, DataSource, and other higher-level DB utilities used in production environments and application servers.

11. java.security

Meaning

Security, cryptography, and access-control APIs.

Utilities

Classes for encryption, keys, certificates, and secure random number generation. Useful for building secure applications and handling authentication/authorization tasks.

12. java.time

Meaning

Modern date & time API introduced in Java 8 (replacement for many java.util.Date use-cases).

Utilities

Types like LocalDate, LocalTime, LocalDateTime, Duration, and Period — with parsing/formatting and timezone support.

13. java.math

Meaning

High-precision numeric classes.

Utilities

BigInteger for arbitrarily large integers and BigDecimal for exact decimal arithmetic — ideal for financial and scientific calculations.

14. javafx.*

Meaning

Modern UI framework for desktop applications (graphics, media, and animation).

Utilities

Packages like javafx.application, javafx.scene, javafx.stage, and javafx.controls to build modern, animated interfaces.

15. java.util.concurrent

Meaning

Concurrency utilities for safer and simpler multithreading.

Utilities

Thread pools (ExecutorService), locks, atomic types, and concurrent collections to build scalable concurrent programs.

16. java.beans

Meaning

JavaBeans component architecture and introspection utilities.

Utilities

Support for property editors, bean introspection, and event handling for reusable components.

17. java.rmi

Meaning

Remote Method Invocation — remote object invocation across JVMs.

Utilities

APIs that allow calling methods on objects located on other machines; used to build distributed Java applications.

Popular posts from this blog

Evolution of computers and Computers today

Image
Who amongst the following is regarded as the creator of the first digital electronic computer? George Boole Alan Turing John V Atanasoff Frederic Calland Williams John von Neumann Solution John Vincent Atanasoff is widely recognized as the creator of the first digital electronic computer. In the late 1930s, along with his graduate student Clifford Berry, he developed the Atanasoff–Berry Computer (ABC) at Iowa State College (now Iowa State University). This machine was completed around 1939–1942. Why the ABC was important: It was the first computing machine to use binary digits (bits) to represent all data. It used electronic vacuum tubes for arithmetic calculations, which made it much faster than mechanical computers. It could solve systems of linear equations, a critical need in engineering and physics. Although the ABC was never fully operational or commercialized like lat...
Read more

Convert into binary

Image
What is/are the binary representation(s) of the decimal number 113? 1110011 1011001 1110000 1110001 0110001 Solution Let’s convert 113 (decimal) into binary step by step: Division by 2 Previous Step Next Step ...
Read more

Processor Types and Specifications

Image
2020-02 Which of the following is/are TRUE regarding the Von Neumann architecture? Single Instruction, Multiple Data (SIMD) Single Program, Multiple Data (SPMD) Single Instruction Stream, Single Data Stream (SISD) Multiple Instruction, Multiple Data (MIMD) Multiple Instruction, Single Data (MISD) Solution The correct option regarding the Von Neumann architecture is (c) Single Instruction Stream, Single Data Stream (SISD) . The Von Neumann architecture is a foundational computer architecture where both data and instructions are stored in the same memory space. This architecture is characterized by a single processing unit that executes instructions sequentially, one at a time, and processes data from a single stream. This aligns with the definition of SISD (Single Instruction, Single Data) in Flynn's Taxonomy, which categorizes computer architectures based on their instruction and data strea...
Read more