Basic Packages of Java

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Basic Packages of Java Utility Classes
java.lang Package java.util Package java.io
Package
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Package

• To group into one unit classes and interfaces
  related to each other
• Provide packages for classes or interfaces to be
  used frequently
• Basic Packages
• java.lang, java.util, java.io, java.net, java.awt
  

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Java Basic Packages
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JDK Packages
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java.lang Package

• Included by Java Compiler without import
  statement
• Interfaces and Classes provided by java.lang
  package

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java.lang Package

• Math Class
• Provide the methods and constants for the
  mathematic calculation
• MathClass.java
• Runtime Class
• Methods to interface between program execution
  environment and programs
• RuntimeClass.java

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java.lang Package

• Thread Class
• Class with methods for implementing a
  multi-thread program
• ThreadGroup Class
• Class to deal with threads as a group
• Class class
• To give information about class or interface
  related to specific object

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java.util Package

• Package to provide useful utility class
• Provide a class to support various standard
  programming data structure
• Package Structure
• Hierarchical Structure of Package

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java.util Package

• Enumeration Interface
• Interface for dealing with the enumerated
  elements
• EnumerationInterface.java
• BitSet Class
• Class to deal with bit set resizing dynamically
• BitSetClass.java
• Vector Class
• Class providing data structures having the
  elements to be accessed through integer index as
  array
• VectorClass.java

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java.util Package

• Stack Class
• Provide methods to manage a stack
• StackClass.java
• Hashtable Class
• Manage a Hashtable to store data and search it
  using given key
• HashtableClass.java
• Random Class
• Methods to generate the random number
• RandomClass.java

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java.util Package

• StringTokenizer Class
• To give the methods to tokenize a given string by
  delimiter such as blank or specified string
• StringTokenizerClass.java
• Date Class
• Class with the methods related to date and time

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java.io Package

• I/O Function based on Stream Class
• Carried out I/O independent off specific OS
• Abstract Class InputStream, OutputStream
• Hierarchical Structure of Class
• Interfaces and Classes included in Package

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java.io Package

• InputStream Class
• Super Class of all InputStream Class
• Abstract Class to provide basic methods related
  to input
• OutputStream Class
• Abstract Class providing the basic methods
  related to output

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java.io Package

• DataInputStream DataOutputStream Class
• Class to define the methods carrying out I/O to
  basic type
• Class implemented by being inherited from
  DataInput interface and DataOutput interface

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java.io Package

• PipedInputStream class PipedOutputStream class
• Class to use the output of one thread as the
  input of other thread
• BufferedInputStream BufferedOutputStream Class
• Place a buffer in the middle of I/O operation to
  avoid direct access to I/O stream

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java.io Package

• FileInputStream FileOutputStream Class
• FileInputStream Class
• To read the data from file
• If cannot open file, Throw FileNotFoundException
• FileOutputStream Class
• To write the data to file
• FilterInputStream FilterOutputStream Class
• Give methods to modify the data additionally when
  reading/writing data

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java.io Package

• ByteArrayInputStream ByteArrayOutputStream
  Class
• Class to use byte array as input object of input
  stream or output object of output stream
• Not blocked, unlike other I/O streams
• PrintStream Class
• To output the data as text form, this was
  implemented by extending FilterOutputStream class

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java.io Package

• File RandomAccessFile Class
• File Class
• Provide abstraction to deal with the file name
  and path name dependent on the host platform as a
  file name and path name independent of the
  machine
• RandomAccessFile Class
• Provide random access file system to support the
  various mechanisms than FileStream does

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java.io Package(Example)

• FileInputStream
• FileInputStream stream variable new
  FileInputStream(file Specification)
• InputStreamReader reader variable new
  InputStreamReader(stream variable)
• StreamTokenizer token_variable new
  StreamTokenizer(reader_variable)
• FileOutputStream
• FileOutputStream stream variable new
  FileOutputStream(file Specification)
• PrinterWriter printer variable new
  PrinterWriter(stream variable)
• Example StreamTest.java
• IO Package will be explained in I/O Stream Chapter