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Introduction to Java FileInputStream

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The following is the declaration forjava.io.FileInputStream class.

public class FileInputStream extends InputStream { }

The above is the syntax of the FileInputStream, where it is extended to the InputStream class.

FileInputStreamclass member Functions : The FileInputStream class contains constructors and some functions as a FileInputStream class member function.

Constructors of Java FileInputStream Class

FileInputStream(File file ): This constructor creates an instance of FileInputstreamby opening a connection to a specified file to read from this instance.

FileInputStream(FileDescriptorfdobj): This constructor creates an instance of FileInputstream by using the file descriptor fdobj, which specifies an existing connection to an actual specified file in the file system to read from this instance.

FileInputStream(String fname): This constructor creates an instance of FileInputstream by opening a connection to a specified file fname parameter to read from this instance.

Functions of Java FileInputStream Class

Function and syntax are given below:

1. read()

This function is used to read a byte of data from the input stream.

public int read() throws IOException 2. read(byte[] b )

This function is used to read bytes of data up to b array size from the input stream.

public int read(byte[] b)throws IOException 3. read(byte[] b, int off, intlen)

This function is used to read bytes of data from the input stream up to specified len into destination b array at start offset.

public int read(byte[] b, int offset, intlen) throws IOException 4. available()

This function is used to return the estimated number of bytes that can be read from the input stream.

public int available() throws IOException 5. skip( long n )

This function is used to skip n bytes of data from the input stream.

public long skip(long n) throws IOException 6. getChannel()

This function is used to get the unique FileChannel object of the file input stream.

public FileChannelgetChannel() 7. finalize() protected void finalize() throws IOException 8. getFD() – T

his function is used to get the FileDescriptor object, which specifies the connection to the file system’s actual file.

public final FileDescriptorgetFD() throws IOException 9. close()

This function is used to close the File stream and release the resource file.

public void close() throws IOException Functions and Examples of File Input Stream Class

Working and examples for the FileInputStream class and its methods in java:

Next, we write the java code to understand the FileInputStream class more clearly with the following example where we create a FileInputStream object by using the FileInputStream class constructor and pass the file name to read a character, as below –

Example #1

Code:

import java.io.FileInputStream; public class Demo { public static void main( String[] arg) { int i; char c; try{ FileInputStream fobj=new FileInputStream("D:\data.txt"); i = fobj.read(); c = (char) i; System.out.println("The First byte is :" +c); System.out.println("The Number of remaining bytes are :" +fobj.available()); fobj.skip(3); i = fobj.read(); c = (char) i; System.out.println("The Next byte after 3 byte skip is :" +c); fobj.close(); }catch(Exception e) { System.out.println(e); } } }

Output:

Example #2

Code:

import java.io.FileInputStream; public class Demo { public static void main( String[] arg) { int i; char c; try { FileInputStream fobj=new FileInputStream("D:\data.txt"); while((i = fobj.read())!=-1) { c = (char) i; System.out.print(c); } System.out.println("nThe unique FileChannel object is : " +fobj.getChannel()); System.out.println("The FileDescriptor object is : " +fobj.getFD()); fobj.close(); }catch(Exception e) { System.out.println(e); } } }

Output:

Example #3

Next, we write the java code to understand the FileInputStream class where we read the data into the byte array, and we extend the user define class to FileInputStream class to use the finalize() method, as below –

Code:

import java.io.FileInputStream; public class Demo extends FileInputStream { public Demo(String file) throws Exception { super(file); } public static void main( String[] arg) { byte[] b = new byte[16]; int i; char c; try { Demo fobj=new Demo("D:\data.txt"); i = fobj.read(b, 1, 15); System.out.println("The total bytes read are : "+i); System.out.print("The bytes read are : "); for(byte t : b) { c = (char)t; System.out.print(c); } fobj.finalize(); fobj.close(); }catch(Exception e) { System.out.println(e); } } }

Output: