FileInputStream class extracts input bytes from a file in a file system. FileInputStream is meant for reading streams of raw bytes such as image data. For reading streams of characters, consider using FileReader. It should be used to read byte-oriented data for example to read audio, video, images, etc. The hierarchy of classes to deal with Input streams is as follows:
Example 1:
// Java program to demonstrate Use of FileInputStream class // Importing the desired class import java.io.FileInputStream;
// Importing input output class from java.io package import java.io.IOException;
// Main class class FileInputStreamGFG {
// Method 1
// To read from the file
private void readFile() throws IOException
{
// Creating an object of FileInputStream
FileInputStream fileInputStream = null ;
// Try block to check for exceptions
try {
// Now, creating a FileInputStream by
// opening a connection to an actual file
// The file named by the path name in the
// file system
// Here customly we have taken
// gfg.txt contains fileInputStream
= new FileInputStream( "gfg.txt" );
// data - "Java was called
// Oak at the beginning."
int i;
// Reads a byte of data from this input stream
// using read() method
// Till condition holds true
while ((i = fileInputStream.read()) != - 1 ) {
// Print the stream
System.out.print(( char )i);
}
}
// If there is any exception encountered
// then execute this block
finally {
// Stream is not there in file
if (fileInputStream != null ) {
// Then close this file input stream and
// releases any system resources associated
// with the stream using close() method
fileInputStream.close();
}
}
}
// Method 2
// Main driver method
public static void main(String[] args)
throws IOException
{
// Constructor of this class
FileInputStreamGFG fileInputStreamGfg
= new FileInputStreamGFG();
// Calling the readFile() method
// in the main() method
fileInputStreamGfg.readFile();
}
} |
Output :
Java was called Oak at the beginning.
Now dwelling onto the output stream that is ObjectInputStream is used for deserializing primitive data and objects previously written using an ObjectOutputStream. Only objects that support the java.io.Externalizable interface can be read from streams. The Java ObjectInputStream class enables you to read Java objects from an InputStream instead of just raw bytes. You wrap an InputStream in an ObjectInputStream and so that you can read objects from it. Of course, the bytes read must represent a valid, serialized Java object. Otherwise, reading objects will fail. Normally we will use the ObjectInputStream to read data objects written(serialized) by a Java ObjectOutputStream.
Example 2:
// Java program to demonstrate Use of ObjectInputStream // class // Importing required input output classes import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
// Before serialization and de-serialization of objects the // class of the object must implement java.io.Serializable // Class 1 // Helper class implementing Serializable interface class Student implements Serializable {
// Private class member variables
private static final long serialVersionUID
= -1438960132000208485L;
private String name;
private int age;
// Constructor of this class
public Student(String name, int age)
{
// super keyword refers to parent class
super ();
// this keyword refers to current object instance
this .name = name;
this .age = age;
}
// Getters and Setter for class
public String getName() { return name; }
public void setName(String name) { this .name = name; }
public int getAge() { return age; }
public void setAge( int age) { this .age = age; }
// Override toString method
@Override public String toString()
{
// Simply return the name and age
return "Student [name=" + name + ", age=" + age
+ "]" ;
}
} // Class 2 // Main class public class ObjectInputStreamDemo {
// Main driver method
public static void main(String[] args)
throws FileNotFoundException, IOException,
ClassNotFoundException
{
// Creating an object of above class
// in the main() method
ObjectInputStreamDemo objectInputStreamDemo
= new ObjectInputStreamDemo();
// Readfile function call
objectInputStreamDemo.readStudentObject();
}
// Member method of main class
private void readStudentObject()
throws IOException, FileNotFoundException,
ClassNotFoundException
{
// Initially null is set to both streams
// read and write streams
FileInputStream fileInputStream = null ;
ObjectInputStream objectInputStream = null ;
// Try block to check for exceptions
try {
// Input stream directory
fileInputStream
= new FileInputStream( "student.txt" );
// Input stream object
objectInputStream
= new ObjectInputStream(fileInputStream);
// Creating an object of above class to
// read an object from the ObjectInputStream
Student student
= (Student)objectInputStream.readObject();
// Display message when input stream is
// completely read
System.out.println(
"Successfully read student object from the file." );
// Print an display commands
System.out.println(student);
System.out.println( "Name = "
+ student.getName());
System.out.println( "Age = "
+ student.getAge());
}
// When an exception is encountered execute the
// block
finally {
// If there is nothing to be read
if (objectInputStream != null ) {
// Then close a ObjectInputStream will
// the InputStream instance from which
// the ObjectInputStream is reading
// isong the close() method
objectInputStream.close();
}
}
}
} |
Output:
Successfully read student object from the file. Student [name=John, age=25] Name = John Age = 25
The only difference between FileInputStream and ObjectInputStream is :
FileInputStream | ObjectInputStream |
---|---|
The Java FileInputStream class, in java.io.FileInputStream, makes it possible to read the contents of a file as a stream of bytes, hence FileInputStream can be used for Serialization. | ObjectInputStream in Java can be used to convert InputStream to object. This process of conversion of the input stream to an object is called deserialization. |
The Java FileInputStream class obtains input bytes from a file. | It can also be used to pass the objects between hosts by using a SocketStream. |
It is used for reading byte-oriented data. | It is mainly used to deserialize the primitive data and objects which are written by using ObjectOutputStream. |
The FileInputStream class contains 9 methods. | The ObjectInputStrean class contains 27 methods. |