I/O

class PrintWriter / PrintStream

• It provides us simple print & println methods to write different type of primitive values as text into output stream(Writer).
• The difference between PrintWriter and PrintStream is that PrintWriter internally uses Writer and PrintStream uses OutputStream.

• PrintWriter(File file)
• PrintWriter(String fileName)
• Creates a new PrintWriter to write contents into file.
• PrintWriter(OutputStream out)
• Creates a new PrintWriter to write into OutputStream.

• PrintStream(File file)
• PrintStream(String fileName)
• PrintStream(OutputStream out)

• void print(int i)
• Prints an integer.
• void print(long l)
• Prints a loninteger.
• void print(Object obj)
• Prints an object
• void print(String s)
• Prints a string.
• void println(int i)
• Prints an integer and new line char.
• void println(long l)
• Prints a long integer and new line char
• void println(Object obj)
• Prints an object and new line char.
• void println(String s)
• Prints a string and new line char

 import java.io.*;
 class demo
 {
    public static void main(String args[])throws Exception
	  {
	    int arr[]={134654665,284976359,375696944,478499493,588388383,
		   698876566,764545453,855454545,978656544,107474733};

	    PrintStream ps=new PrintStream("c:/temp/num.lst");
	    for(int i=0;i<arr.length;i++)
		    ps.println(arr[i]);
	    ps.close();
	    System.out.println("Data Stored...");
	  }
 }

Data Stored...

Serialization

• Serialization is a mechanism of storing an object into a byte stream.
• The object which we want to write into byte Stream must be serializable i.e it must be implemented from a marker interface Serializable.
• To achieve serialization java provides us an class ObjectOutputStream to write objects into byte Stream.

Interface Serializable

• It is a marker interface.
• A Marker Interface does not have any methods and fields.
• Thus classes implementing it do not have to implement any methods.
• Classes implement it if they want their Objects to be Serialized or Deserialized.

 import java.io.Serializable;
 class Student implements Serializable
 {
  private int rollno;
  private String name;
  public Student(int rn,String nm)
	{
	  rollno=rn;
	  name=nm;
	}
  public void showData()
	{
	  System.out.println("Rollno is "+rollno);
	  System.out.println("Name is "+name);
	}
 }

Class ObjectOutputStream

• It is an Wrapper to write objects and different types of values into outputstream.

• ObjectOutputStream(OutputStream out)
• creates an ObjectOutputStream that writes to the specified OutputStream

• void writeObject(Object obj)
• writes the specified object to the ObjectOutputStream.
• void writeInt(int n)
• writes the specified int value to the ObjectOutputStream.
• void writeLong(long n)
• writes the specified long value to the ObjectOutputStream.
• void writeFloat(float n)
• writes the specified float value to the ObjectOutputStream.
• void close()
• closes the current output stream.

 import java.io.*;
 class demo
 {
  public static void main(String args[])throws Exception
  {
    Student a=new Student(4117,"Amit jain");
    Student b=new Student(3012,"Gopal pandey");
    Student c=new Student(5126,"Mona Mantri");
    FileOutputStream fout=new FileOutputStream("c:/temp/stud.lst");
    ObjectOutputStream os=new ObjectOutputStream(fout);
    os.writeObject(a);
    os.writeObject(b);
    os.writeObject(c);
    os.close();
    fout.close();
    System.out.println("objects saved....");
  }
 }

Data Stored...

De-Serialization

• Deserialization is a mechanism of reading object from a byte stream.
• To achieve deserialization java provides us an class ObjectInputStream to read objects from byte Stream.

Class ObjectInputStream

• It is an Wrapper to read objects and different types of values from inputstream.

• ObjectInputStream(InputStream in)
• creates an ObjectInputStream that reads from the specified InputStream.

• Object readObject()
• reads an object from the input stream.
• int readInt()
• read an int value from Stream.
• long readLong()
• read an long value from Stream.
• float readFloat()
• read an float value from Stream.
• double readDouble()
• read an double value from Stream.
• void close()
• closes ObjectInputStream.

 import java.io.*;
 class demo
 {
  public static void main(String args[])throws Exception
	{
	  FileInputStream fin=new FileInputStream("c:/temp/stud.lst");
	  ObjectInputStream os=new ObjectInputStream(fin);
	  Student x=(Student)os.readObject();
	  Student y=(Student)os.readObject();
	  Student z=(Student)os.readObject();
	  os.close();
	  fin.close();
	  x.showData();
	  y.showData();
	  z.showData();
	}
 }