Java Standard Libraries

Java has a large number of libraries that are included with the JDK. These libraries are known as the Java Standard Libraries. They are divided into packages and classes. The Java Standard Libraries are organized into packages. Each package contains a set of related classes. The Java Standard Libraries are grouped into several packages. Some of the most important packages are:

• java.lang - Contains classes that are fundamental to the design of the Java programming language. The most important classes in this package are Object, String, StringBuffer, System, Thread, Math, Integer, Float, Double, Boolean, and Character.

• java.util - Contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, a random-number generator, and a bit array).

• java.io - Contains classes for input and output operations.

• java.net - Contains classes for networking.

• java.awt - Contains classes for creating user interfaces and for painting graphics and images.

• javax.swing - Contains classes for creating user interfaces.

• java.applet - Contains classes for creating applets.

• java.sql - Contains classes for accessing and processing data stored in a database.

• java.rmi - Contains classes for creating remote method invocation objects.

• java.security - Contains classes for implementing security.

• java.text - Contains classes for formatting and parsing numbers, dates, and text.

• java.util.regex - Contains classes for matching patterns in strings.

• java.util.concurrent - Contains classes for concurrent programming.

• java.util.stream - Contains classes for processing sequences of elements.

• java.nio - Contains classes for performing input and output operations.

• java.time - Contains classes for working with dates and times.

• java.lang.reflect - Contains classes for obtaining information about classes and objects.

• java.lang.annotation - Contains classes for creating and processing annotations.

• java.lang.instrument - Contains classes for monitoring and controlling the JVM.

• java.lang.management - Contains classes for managing and monitoring the JVM.

• java.lang.invoke - Contains classes for implementing dynamic method invocation.

• java.lang.module - Contains classes for working with modules.

• java.lang.ref - Contains classes for implementing reference objects.

java.lang Package

The java.lang package is automatically imported into every Java program. This package contains classes that are fundamental to the design of the Java programming language. Some of the most important classes in this package are:

• Object - The root class of the Java
• String - Represents a sequence of characters
• StringBuffer - Represents a mutable sequence of characters
• System - Provides access to system resources
• Thread - Represents a thread of execution
• Math - Provides mathematical functions
• Integer - Represents an integer
• Float - Represents a floating-point number
• Double - Represents a double-precision floating-point number
• Boolean - Represents a boolean value
• Character - Represents a character

java.util Package

The java.util package contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes. Some of the most important classes in this package are:

• ArrayList - Implements a dynamic array
• LinkedList - Implements a linked list
• HashMap - Implements a hash table
• HashSet - Implements a hash set
• Hashtable - Implements a hash table
• TreeMap - Implements a red-black tree

java.io Package

The java.io package contains classes for input and output operations. Some of the most important classes in this package are:

• File - Represents a file or directory
• FileInputStream - Reads data from a file
• FileOutputStream - Writes data to a file
• BufferedReader - Reads text from a character-input stream
• BufferedWriter - Writes text to a character-output stream
• DataInputStream - Reads primitive data types from an input stream
• DataOutputStream - Writes primitive data types to an output stream

java.net Package

The java.net package contains classes for networking. Some of the most important classes in this package are:

• URL - Represents a Uniform Resource Locator
• URLConnection - Represents a connection to a URL
• Socket - Represents a socket
• ServerSocket - Represents a server socket

java.awt Package

The java.awt package contains classes for creating user interfaces and for painting graphics and images. Some of the most important classes in this package are:

• Frame - Represents a window
• Panel - Represents a container for components
• Button - Represents a button
• Label - Represents a label
• TextField - Represents a text field
• TextArea - Represents a text area
• Canvas - Represents a canvas for drawing graphics

javax.swing Package

The javax.swing package contains classes for creating user interfaces. Some of the most important classes in this package are:

• JFrame - Represents a window
• JPanel - Represents a container for components
• JButton - Represents a button
• JLabel - Represents a label
• JTextField - Represents a text field
• JTextArea - Represents a text area
• JCanvas - Represents a canvas for drawing graphics

java.applet Package

The java.applet package contains classes for creating applets. Some of the most important classes in this package are:

• Applet - Represents an applet
• AppletContext - Represents the context of an applet
• AppletStub - Represents the stub of an applet

java.sql Package

The java.sql package contains classes for accessing and processing data stored in a database. Some of the most important classes in this package are:

• Connection - Represents a connection to a database
• Statement - Represents a SQL statement
• ResultSet - Represents a result set

java.rmi Package

The java.rmi package contains classes for creating remote method invocation objects. Some of the most important classes in this package are:

• Remote - Represents a remote object
• RemoteException - Represents a remote exception

java.security Package

The java.security package contains classes for implementing security. Some of the most important classes in this package are:

• Key - Represents a cryptographic key
• KeyPair - Represents a key pair
• KeyPairGenerator - Generates key pairs
• KeyStore - Manages keys and certificates
• MessageDigest - Computes a message digest
• Signature - Signs and verifies data

java.text Package

The java.text package contains classes for formatting and parsing numbers, dates, and text. Some of the most important classes in this package are:

• DecimalFormat - Formats decimal numbers
• SimpleDateFormat - Formats dates and times
• MessageFormat - Formats messages

java.util.regex Package

The java.util.regex package contains classes for matching patterns in strings. Some of the most important classes in this package are:

• Pattern - Represents a compiled regular expression
• Matcher - Matches a pattern against a string

java.util.concurrent Package

The java.util.concurrent package contains classes for concurrent programming. Some of the most important classes in this package are:

• Executor - Executes tasks
• ExecutorService - Manages a pool of threads
• Future - Represents the result of an asynchronous computation
• Callable - Represents a task that returns a result
• RunnableFuture - Represents a runnable future

java.util.stream Package

The java.util.stream package contains classes for processing sequences of elements. Some of the most important classes in this package are:

• Stream - Represents a sequence of elements
• Collector - Collects elements into a container
• Supplier - Supplies elements
• Consumer - Consumes elements
• Function - Transforms elements
• Predicate - Tests elements

java.nio Package

The java.nio package contains classes for performing input and output operations. Some of the most important classes in this package are:

• ByteBuffer - Represents a byte buffer
• CharBuffer - Represents a character buffer
• ShortBuffer - Represents a short buffer

java.time Package

The java.time package contains classes for working with dates and times. Some of the most important classes in this package are:

• LocalDate - Represents a date
• LocalTime - Represents a time
• LocalDateTime - Represents a date and time
• ZonedDateTime - Represents a date and time with a time zone
• Duration - Represents a duration
• Period - Represents a period

java.lang.reflect Package

The java.lang.reflect package contains classes for obtaining information about classes and objects. Some of the most important classes in this package are:

• Class - Represents a class
• Field - Represents a field
• Method - Represents a method
• Constructor - Represents a constructor

java.lang.annotation Package

The java.lang.annotation package contains classes for creating and processing annotations. Some of the most important classes in this package are:

• Annotation - Represents an annotation
• AnnotationType - Represents an annotation type

java.lang.instrument Package

The java.lang.instrument package contains classes for monitoring and controlling the JVM. Some of the most important classes in this package are:

• Instrumentation - Provides services for monitoring and controlling the JVM

java.lang.management Package

The java.lang.management package contains classes for managing and monitoring the JVM. Some of the most important classes in this package are:

• MemoryMXBean - Represents the memory management of the JVM
• ThreadMXBean - Represents the thread management of the JVM

java.lang.invoke Package

The java.lang.invoke package contains classes for implementing dynamic method invocation. Some of the most important classes in this package are:

• MethodHandle - Represents a method handle
• MethodType - Represents a method type

java.lang.module Package

The java.lang.module package contains classes for working with modules. Some of the most important classes in this package are:

• Module - Represents a module
• ModuleLayer - Represents a layer of modules

java.lang.ref Package

The java.lang.ref package contains classes for implementing reference objects. Some of the most important classes in this package are:

• Reference - Represents a reference object
• SoftReference - Represents a soft reference object

Conclusion

The Java Standard Libraries are a set of libraries that are included with the JDK. They are organized into packages and classes. The Java Standard Libraries are grouped into several packages, each containing a set of related classes. Some of the most important packages are java.lang, java.util, java.io, java.net, java.awt, javax.swing, java.applet, java.sql, java.rmi, java.security, java.text, java.util.regex, java.util.concurrent, java.util.stream, java.nio, java.time, java.lang.reflect, java.lang.annotation, java.lang.instrument, java.lang.management, java.lang.invoke, java.lang.module, and java.lang.ref. These libraries provide a wide range of functionality that can be used to develop Java applications.