Read / write file bit by bit

[Tomita Militaru]

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.