Programming language JAVA Input output opearations

Programming language JAVA Input output opearations

• 1.
  Java I/O
• 2.
  File • Long-term storageof large amounts of data • Persistent data exists a5er termina6on of program • Files stored on secondary storage devices – Magne6c disks – Op6cal disks – Magne6c tapes • Sequen6al and random access files 2
• 3.
  File Class • Providesuseful informa6on about a file or directory • Does not open files or process files • To obtain or manipulate path, 6me, date, permissions etc • Constructor – File(String directoryPath) – File(String directoryPath, String fileName) – File(File dirObj, String fileName) • Example: FileDemo.java 3
• 4.
  Directory Class • Directoriesare also files • Contains list of files and directories • For DirectoryisDirectory() returns true String[] list() – returns an array of strings that gives the files and directories contained File[] listFiles() – Returns array of File objects • Example: DirectoryDemo.java 4
• 5.
  Stream Classes • Javaviews a File as a stream of bytes. – File ends with end-of-file marker or a specific byte number – File as a stream of bytes associated with an object. – Java also associates streams with devices • System.in, System.out, and System.err – Streams can be redirected • Stream is an abstrac6on that either produces or consumes informa6on 5
• 6.
  Stream Classes • Java’sstream-based I/O is built upon four abstract classes. – InputStream, OutputStream (for byte streams) – Reader, Writer (for character streams) • They form separate hierarchies • Use the character stream classes when working with characters or strings • Use the byte stream classes when working with bytes or other binary objects 6
• 7.
  Byte Stream Classes •Byte-Stream classes are topped by InputStream and OutputStream classes • InputStream is an abstract class that defines Java’s model of streaming byte input. int available() void close() int read() int read(byte buff[]) int read(byte buff[], int off, int num) • OutputStream is an abstract class that defines Java’s model of streaming byte output. void flush() void close() void write(int b) void write(byte buff[]) void write(byte buff[], int off, int num) 7
• 8.
  FileInputStream • FileInputStream classcreates an InputStream that you can use to read bytes from a file • Constructors – FileInputStream(String filePath) – FileInputStream(File fileObj) • Example: FileInputStreamDemo.java 8
• 9.
  FileOutputStream • FileOutputStream classcreates an OutputStream that you can use to write bytes to a file • Constructors – FileOutputStream(String filePath) – FileOutputStream(File fileObj) – FileOutputStream(String path, boolean append) – FileOutputStream(File obj, boolean append) • Example: FileOutputStreamDemo.java, FileCopyDemo.java 9
• 10.
  Character Streams • CharacterStream classes are topped by Reader and Writer class • Reader is an abstract class that defines Java’s model of streaming character input void close() int read() int read(char buff[]) int read(char buff[], int off, int num) • Writer is an abstract class that defines Java’s model of streaming character output void flush() void close() void write(int ch) void write(char buff[]) void write(char buff[], int off, int num) void write(String s) void write(String s, int off, int num) 10
• 11.
  FileReader • FileReader classcreates a Reader that you can use to read the contents of a file • Constructors – FileReader(String filePath) – FileReader(File fileObj) • Example: FileReaderDemo.java 11
• 12.
  FileWriter • FileWriter classcreates a Writer that you can use to write to a file • Constructors – FileWriter(String filePath) – FileWriter(File fileObj) – FileWriter(String path, boolean append) – FileWriter(File obj, boolean append) • Example: FileWriterDemo.java 12
• 13.
  BufferedReader • BufferedReader isa Reader that buffers input • It improves performance by reducing the number of 6mes data us actually physically read from the input stream • Constructors – BufferedReader(Reader reader) – BufferedReader(Reader reader, int buffSize) • Example: BufferedReaderDemo.java 13
• 14.
  BufferedWriter • BufferedWriter isa Writer that buffers output • It improves performance by reducing the number of 6mes data actually physically wricen to the output stream • Constructors – BufferedWriter(Writer writer) – BufferedWriter(Writer writer, int buffSize) • Example: BufferedWriterDemo.java 14
• 15.
  Serializa6on • Serializa6on isthe process of wri6ng the state of an object to a byte stream – This is useful when you want to save the state of your program to a persistent storage such as file – Later these objects can be restored by using the process of deserializa6on • Serializa6on can be achieved by implemen6ng Serializable interface 15
• 16.
  Object(Input/Output)Stream • ObjectInputStream classextends the InputStream class • It is responsible for reading objects from a stream • ObjectOutputStream class extends the OutputStream class • It is responsible for wri6ng objects to a stream • Example: ObjectSerializaJonDemo.java 16
• 17.
  Self Study
• 18.
  Data(Input/Output)Stream • DataInputStream &DataOutputStream enable to write or read primi6ve data to or from a stream • They implement the DataOutput & DataInput interfaces respec6vely • Constructors – DataOutputStream(OutputStream os) – DataInputStream(InputStream is) • Example: DataIODemo.java 18
• 19.
  Console • It isused to read and write to the console • It supplies no constructor. A Console object is obtained by calling System.console() • Important Methods – prinf, – readLine – readPassword • Example: ConsoleDemo.java 19
• 20.
  RandomAccessFile 20