Java Tutorial : Java IO (Java PushbackReader-example) ~ foundjava

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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

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