Read / write file bit by bit

Hello,
I need to do this assignment in which I need to read / write from / to a file bit by bit using a buffer. When the buffer has 8 bits, I write a byte to the file, same for reading.
Here is why I did so far, I'm using String for reading/writing and I'm sure this is not a good/eficient way to do it. If there is another way can someone please suggest, I don't need the solution directly, just some hints. Thanks

import java.io.BufferedInputStream;

import java.io.BufferedWriter;

import java.io.DataInputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.FileWriter;

import java.io.IOException;


/**

 * Operations read / write by bit

 * @author Tomita Militaru

 * 

 */

public class BitOperations {

	/**

	 * Buffer to keep read stuff

	 */

	static String readBuffer = "";

	/**

	 * Buffer to keep write stuff

	 */

	static String writeBuffer = "";

	static int readCounter = 0;

	static int writeCounter = 8;

	private static int nextByte = 0;


	/**

	 * My method to write a bit to a file

	 * 

	 * @param value

	 */

	public static void writeBits() {

		try {

			FileOutputStream output = new FileOutputStream("output.txt");

			Byte value_Byte = Byte.valueOf(writeBuffer);

			output.write(value_Byte);

			output.close();

		} catch (Exception e) {

			System.err.println("Error: " + e.getMessage());

		}

	}


	public static void writeBit(int bit) {

		if (writeCounter != 0) {

			writeCounter--;

		} else {

			writeBits();

			writeBuffer = "";

		}

		writeBuffer = writeBuffer.concat(String.valueOf(bit));

	}


	/**

	 * My method to return a bit from a file

	 * 

	 * @return a bit

	 */

	public static void readBits() {

		File file = new File("input.txt");

		FileInputStream fis = null;

		BufferedInputStream bis = null;

		DataInputStream dis = null;

		byte continut = 0;

		int k = 0;

		readCounter = 7;

		try {

			fis = new FileInputStream(file);


			bis = new BufferedInputStream(fis);

			dis = new DataInputStream(bis);


			while (dis.available() != 0 && k <= nextByte) {

				continut = dis.readByte();

				Byte continut_Byte = new Byte("10");

				readBuffer = Integer.toBinaryString(continut_Byte.intValue());

				k++;

			}

			nextByte++;

			fis.close();

			bis.close();

			dis.close();


		} catch (FileNotFoundException e) {

			e.printStackTrace();

		} catch (IOException e) {

			e.printStackTrace();

		}

	}


	public static int readBit() {

		int readBufferLenght = readBuffer.length();

		System.out.println("readbuffer: " + readBufferLenght);

		if (readCounter != 0) {

			int pos = readBuffer.length() - readCounter--;

			System.out.println("pos: " + pos);

			return Integer.parseInt(readBuffer.substring(pos, pos + 1));

		} else {

			readBits();

			return readBit();

		}

	}


	/**

	 * @param args

	 */

	public static void main(String[] args) {

		for (int i = 0; i < 64; i++) {

			writeBit(readBit()); //just for testing, basically i simulate a copy/paste from one file to another.

		}

	}


}

The read method works, but I would like to rewrite the class using another method do it.