Java Tutorial : Java IO (Java File | Java File Class)-Playlist

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Java Tutorial : Java IO (Java File | Java File Class)

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Java Tutorial : Java IO (Java File | Java File Class) 

Java Tutorial : Java IO (Java File | Java File Class) 

Java Tutorial : Java IO (Java File | Java File Class) 

Java Tutorial : Java IO (Java File | Java File Class) 

Java Tutorial : Java IO (Java File | Java File Class) 

Java Tutorial : Java IO (Java File | Java File Class) 

Refer: 
https://docs.oracle.com/javase/8/docs/api/index.html?java/io/File.html
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Java Tutorial : Java IO (Java PushbackInputStream-example)

Click here to watch in Youtube : 
https://www.youtube.com/watch?v=5kn8_SHVI9s&list=UUhwKlOVR041tngjerWxVccw

myfile.txt

Hello world

PushbackInputStreamDemo.java

import java.io.FileInputStream;
import java.io.IOException;
import java.io.PushbackInputStream;

/*
 * public PushbackInputStream(InputStream in, int size)
 * 
 * Parameters:
 * -----------
 * 
 * in - the input stream from which bytes will be read.
 * size - the size of the pushback buffer.
 */
public class PushbackInputStreamDemo
{

    public static void main(String[] args) throws IOException
    {
        FileInputStream fileInputStream = null;
        PushbackInputStream pushbackInputStream = null;
        try
        {
            fileInputStream = new FileInputStream("myfile.txt");

            /*
             * Creates a PushbackInputStream with a pushback
             * buffer of the specified size, and saves its
             * argument, the input stream in, for later use.
             */
            pushbackInputStream = new PushbackInputStream(fileInputStream, 8);

            byte[] byteArray = new byte[10];
            
            /*
             * Reads up to len bytes of data from this input
             * stream into an array of bytes.
             */
            int numberOfBytesRead = pushbackInputStream.read(byteArray, 0, 5);
        
            System.out.println("numberOfBytesRead = "+numberOfBytesRead);
            System.out.println(new String(byteArray));

            /*
             * Pushes back a portion of an array of bytes by
             * copying it to the front of the pushback
             * buffer.
             */
            pushbackInputStream.unread(byteArray, 0, 5);

            numberOfBytesRead = pushbackInputStream.read(byteArray, 0, 5);
            System.out.println("numberOfBytesRead = "+numberOfBytesRead);
            System.out.println(new String(byteArray));

        }
        finally
        {
            if (pushbackInputStream != null)
            {
                /*
                 * Closing a PushbackInputStream will also
                 * close the Reader instance from which the
                 * PushbackInputStream is reading.
                 */
                pushbackInputStream.close();
            }
        }
    }

}

Output

numberOfBytesRead = 5
Hello
numberOfBytesRead = 5
Hello

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Github Link:
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Bitbucket Link:
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Java Tutorial : Java IO (Java PushbackInputStream)-Playlist

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Java Tutorial : Java IO (Java PushbackInputStream)

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Java Tutorial : Java IO (Java PushbackInputStream) 

Java Tutorial : Java IO (Java PushbackInputStream) 

Java Tutorial : Java IO (Java PushbackInputStream) 

myfile.txt

Hello world

PushbackInputStreamDemo.java

import java.io.FileInputStream;
import java.io.IOException;
import java.io.PushbackInputStream;

public class PushbackInputStreamDemo
{

    public static void main(String[] args) throws IOException
    {
        FileInputStream fileInputStream = null;
        PushbackInputStream pushbackInputStream = null;
        try
        {
            fileInputStream = new FileInputStream("myfile.txt");
            pushbackInputStream = new PushbackInputStream(fileInputStream);

            /*
             * Reads the next byte of data from this input
             * stream.
             */
            int data = pushbackInputStream.read();
            System.out.println((char) data);

            /*
             * Pushes back a byte by copying it to the front
             * of the pushback buffer.
             */
            pushbackInputStream.unread(data);

            data = pushbackInputStream.read();
            System.out.println((char) data);

        }
        finally
        {
            if (pushbackInputStream != null)
            {
                /*
                 * Closing a pushbackInputStream will also
                 * close the FileInputStream instance from
                 * which the PushbackReader is reading.
                 */
                pushbackInputStream.close();
            }
        }

    }

}

Output

H
H

Refer: 
https://docs.oracle.com/javase/8/docs/api/java/io/PushbackInputStream.html

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/JavaIODemo_PushbackInputStream_App.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/JavaIODemo_PushbackInputStream_App

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/1915a31f5d5a00376375704c121f0a5c57372292/BasicJava/JavaIODemo_PushbackInputStream_App/?at=master

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Java Tutorial : Java IO (Java PushbackReader-example)

Click here to watch in Youtube : 
https://www.youtube.com/watch?v=33qwWZ1ECSY&list=UUhwKlOVR041tngjerWxVccw

myfile.txt

Hello world

PushbackReaderDemo.java

import java.io.FileReader;
import java.io.IOException;
import java.io.PushbackReader;

/*
 * public PushbackReader(Reader in, int size)
 * 
 * Parameters: 
 * ---------- 
 * in - The reader from which characters will be read 
 * size - The size of the pushback buffer
 */
public class PushbackReaderDemo
{

    public static void main(String[] args) throws IOException
    {
        FileReader fileReader = null;
        PushbackReader pushbackReader = null;
        try
        {
            fileReader = new FileReader("myfile.txt");
            /*
             * Creates a new pushback reader with a pushback
             * buffer of the given size.
             */
            pushbackReader = new PushbackReader(fileReader, 8);

            char[] charArray = new char[10];
            /*
             * Reads characters into a portion of an array.
             */
            int numberOfCharsRead = pushbackReader.read(charArray, 0, 5);
            System.out.println("numberOfCharsRead = "+numberOfCharsRead);
            System.out.println(new String(charArray));

            /*
             * Pushes back a portion of an array of
             * characters by copying it to the front of the
             * pushback buffer.
             */
            pushbackReader.unread(charArray, 0, 5);

            numberOfCharsRead = pushbackReader.read(charArray, 0, 5);
            System.out.println("numberOfCharsRead = "+numberOfCharsRead);
            System.out.println(new String(charArray));

        }
        finally
        {
            if (pushbackReader != null)
            {
                /*
                 * Closing a PushbackReader will also close
                 * the Reader instance from which the
                 * PushbackReader is reading.
                 */
                pushbackReader.close();
            }
        }

    }

}

Output

numberOfCharsRead = 5
Hello
numberOfCharsRead = 5
Hello

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/JavaIODemo_PushbackReader_Example_App.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/JavaIODemo_PushbackReader_Example_App

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/afab0ff1466aae3a6d02c0935e804f2f099cf483/BasicJava/JavaIODemo_PushbackReader_Example_App/?at=master

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Java Tutorial : Java IO (Java PushbackReader) - Playlist

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Java Tutorial : Java IO (Java PushbackReader)

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Click the below Image to Enlarge

Java Tutorial : Java IO (Java PushbackReader) 

Java Tutorial : Java IO (Java PushbackReader) 

Java Tutorial : Java IO (Java PushbackReader) 

myfile.txt

Hello world

PushbackReaderDemo.java

import java.io.FileReader;
import java.io.IOException;
import java.io.PushbackReader;

public class PushbackReaderDemo
{

    public static void main(String[] args) throws IOException
    {
        FileReader fileReader = null;
        PushbackReader pushbackReader = null;
        try
        {
            fileReader = new FileReader("myfile.txt");
            pushbackReader = new PushbackReader(fileReader);
            int data = pushbackReader.read();
            System.out.println((char) data);

            /*
             * Pushes back a single character by copying it
             * to the front of the pushback buffer. After
             * this method returns, the next character to be
             * read will have the value (char)c.
             */
            pushbackReader.unread(data);

            /*
             * Reads a single character.
             */
            data = pushbackReader.read();
            System.out.println((char) data);

        }
        finally
        {
            if (pushbackReader != null)
            {
                /*
                 * Closing a PushbackReader will also close
                 * the Reader instance from which the
                 * PushbackReader is reading.
                 */
                pushbackReader.close();
            }
        }

    }

}

Output

H
H

Refer:
https://docs.oracle.com/javase/8/docs/api/index.html?java/io/PushbackReader.html

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/JavaIODemo_PushbackReader_App.zip?attredirects=0&d=1
Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/JavaIODemo_PushbackReader_App
Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/afab0ff1466aae3a6d02c0935e804f2f099cf483/BasicJava/JavaIODemo_PushbackReader_App/?at=master

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Java Tutorial : Java IO (Java StreamTokenizer - How to tokenize a word)

Click here to watch in Youtube : 
https://www.youtube.com/watch?v=oL7fVykCUYA&list=UUhwKlOVR041tngjerWxVccw

StreamTokenizerDemo.java

import java.io.IOException;
import java.io.StreamTokenizer;
import java.io.StringReader;

public class StreamTokenizerDemo
{

    public static void main(String[] args) throws IOException
    {
        StringReader stringReader = new StringReader("Peter welcome to India");
        StreamTokenizer tokenizer = new StreamTokenizer(stringReader);
        /*
         * TT_EOL is used to determine end of line
         */
        while (tokenizer.nextToken() != StreamTokenizer.TT_EOF)
        {
            /*
             * sval-The string value of the token, if the
             * token was a string (word)
             */
            System.out.println(tokenizer.sval);
        }

    }

}

Output

Peter
welcome
to
India

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/JavaIODemo_StreamTokenizerDemo_word_App.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/JavaIODemo_StreamTokenizerDemo_word_App

Bitbucket Link:
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Java Tutorial : Java IO (Java StreamTokenizer) - Playlist

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Java Tutorial : Java IO (Java StreamTokenizer - How to tokenize file content)

Click here to watch in Youtube : 
https://www.youtube.com/watch?v=x7LPhfcnTKg&list=UUhwKlOVR041tngjerWxVccw

myfile.txt

Hello, How are you peter?
Shall we go to India. 2+2=4 

StreamTokenizerDemo.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.StreamTokenizer;

public class StreamTokenizerDemo
{

    public static void main(String[] args) throws IOException
    {
        FileReader fileReader = null;
        BufferedReader bufferedReader = null;
        try
        {
            fileReader = new FileReader("myfile.txt");
            bufferedReader = new BufferedReader(fileReader);
            StreamTokenizer st = new StreamTokenizer(bufferedReader);

            // print the stream tokens
            boolean eof = false;
            do
            {
                /*
                 * Parses the next token from the input
                 * stream of this tokenizer. The type of the
                 * next token is returned in the ttype
                 * field. Additional information about the
                 * token may be in the nval field or the
                 * sval field of this tokenizer.
                 *
                 * Typical clients of this class first set
                 * up the syntax tables and then sit in a
                 * loop calling nextToken to parse
                 * successive tokens until TT_EOF is
                 * returned.
                 */
                int token = st.nextToken();
                switch (token)
                {
                case StreamTokenizer.TT_EOF:
                    System.out.println("End of File encountered.");
                    eof = true;
                    break;
                case StreamTokenizer.TT_EOL:
                    System.out.println("End of Line encountered.");
                    System.out.println("Line Number:" + st.lineno());
                    break;
                case StreamTokenizer.TT_WORD:
                    System.out.println("Word: " + st.sval);
                    break;
                case StreamTokenizer.TT_NUMBER:
                    System.out.println("Number: " + st.nval);
                    break;
                default:
                    System.out.println((char) token + " encountered.");
                    if (token == '!')
                    {
                        eof = true;
                    }
                }
            }
            while (!eof);
        }
        finally
        {
            if (bufferedReader != null)
            {
                bufferedReader.close();
            }
        }

    }

}

Output

Word: Hello
, encountered.
Word: How
Word: are
Word: you
Word: peter
? encountered.
Word: Shall
Word: we
Word: go
Word: to
Word: India.
Number: 2.0
+ encountered.
Number: 2.0
= encountered.
Number: 4.0
End of File encountered.

Click the below link to download the code:
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Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/JavaIODemo_StreamTokenizerDemo_file_App

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/afab0ff1466aae3a6d02c0935e804f2f099cf483/BasicJava/JavaIODemo_StreamTokenizerDemo_file_App/?at=master

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Java Tutorial : Java IO (Java StreamTokenizer)

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Click the below Image to Enlarge

Java Tutorial : Java IO (Java StreamTokenizer) 

Java Tutorial : Java IO (Java StreamTokenizer) 

Java Tutorial : Java IO (Java StreamTokenizer) 

Java Tutorial : Java IO (Java StreamTokenizer) 

Java Tutorial : Java IO (Java StreamTokenizer) 

StreamTokenizerDemo.java

import java.io.IOException;
import java.io.StreamTokenizer;
import java.io.StringReader;

public class StreamTokenizerDemo
{

    public static void main(String[] args) throws IOException
    {
        StreamTokenizer streamTokenizer = null;
        StringReader stringReader = new StringReader("Peter had 1 pen.");

        streamTokenizer = new StreamTokenizer(stringReader);

        while (streamTokenizer.nextToken() != StreamTokenizer.TT_EOF)
        {

            if (streamTokenizer.ttype == StreamTokenizer.TT_WORD)
            {
                System.out.println("Inside TT_Word = " + streamTokenizer.sval);
            }
            else if (streamTokenizer.ttype == StreamTokenizer.TT_NUMBER)
            {
                System.out
                        .println("Inside TT_NUMBER = " + streamTokenizer.nval);
            }
        }

    }

}

Output

Inside TT_Word = Peter
Inside TT_Word = had
Inside TT_NUMBER = 1.0
Inside TT_Word = pen.

Refer:
https://docs.oracle.com/javase/8/docs/api/java/io/StreamTokenizer.html

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/JavaIODemo_StreamTokenizerDemo_App.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/JavaIODemo_StreamTokenizerDemo_App

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/afab0ff1466aae3a6d02c0935e804f2f099cf483/BasicJava/JavaIODemo_StreamTokenizerDemo_App/?at=master

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Java Tutorial : Java IO (Java Serialization of Complex Objects)

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What Is Serialization in Java?

Serialization is the process of converting an object's state into a byte stream. This byte stream can then be saved to a file, stored in a database, or transmitted across a network. Deserialization does the exact opposite: it reconstructs the original object from the byte stream.

Handling Complex Object Graphs

In real-world Java applications, objects rarely exist alone. A single object frequently holds references to other objects, creating an object graph:

• Suppose you have Object A, which contains references to Object B and Object C.
• In turn, Object B references Object D and Object E.

When you pass the top-level Object A to the writeObject() method, Java's serialization engine automatically navigates the entire graph. All interconnected objects (A, B, C, D, and E) are written to the output stream together.

Rebuilding the Objects with Deserialization

When reading back using readObject(), Java handles reconstructing the complete network of objects. Crucially, the original object references and relationships are preserved exactly as they were created, ensuring your program's state remains intact.

Watch More Related Java Tutorials

Check out these related Java Serialization tutorials from our channel:

• Understanding Java Serialization | Java IO | Java Tutorial
• Java Serialization with Transient keyword | Java IO | Java Tutorial
• What is Java ObjectInputStream? | Java Serialization | Java IO | Java Tutorial

---

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Java Tutorial : Java IO (Java Serialization of Complex Objects) 

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Java Tutorial : Java IO (Java Serialization and Deserialization notes)

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1. The Transient Keyword and Default Values

When you serialize an object, you might not want every single field saved. If you declare a field as transient, Java will skip it during serialization.

Upon deserialization, transient fields automatically receive their language defaults:

• Object references (like String) are set to null.
• Numeric types (like int) are initialized to 0.
• Boolean fields are initialized to false.

2. Why Static Variables Are Not Serialized

A common question in Java interviews is whether static fields are serialized. The short answer is no. Serialization preserves the state of a specific object instance. Because static variables belong to the class itself rather than any individual instance, they are not saved into the byte stream.

3. Object Graph Traversal & NotSerializableException

During serialization, the runtime navigates the entire object graph. If an encountered object does not implement java.io.Serializable, the JVM throws a NotSerializableException indicating the offending class.

The Fix: If you cannot modify that class to make it serializable, declare the reference holding that object as transient.

Watch More Related Java Tutorials

Deepen your understanding of Java IO and serialization with these tutorials:

• Java Serialization Rules Explained | Java IO | Java Tutorial
• What is Java Serialization with IS-A Inheritance? | Java IO | Java Tutorial
• How to Serialize Primitive Values in Java? | Java Serialization | Java IO | Java Tutorial

---

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