/**
 * Represents a string of bit values (0 or 1)
 * @
 */
public class StringOfBits extends Object {
    private StringOfBits sb;
    private CharSequence chars;
    /**
     * Constructs the empty bit string ; length() == 0
     */

    public StringOfBits() {
        this.sb = null;
        this.chars = null;
    }
    /**
     * Copy constructor
     * @param sb
     */
    public StringOfBits(StringOfBits sb){
        this.chars = null;
        this.sb = sb;
    }

    /**
     * Constructs a bit string from a sequence of '0' and '1' characters.  If
     * the parameter is not comprised of '0' and '1' characters the behavior
     * is undefined.
     *
     * @param chars the sequence to convert into bits
     */

    public StringOfBits(CharSequence chars){
        this.sb = null;
        this.chars = chars;
    }

    /**
     * Returns the length of this bit string
     * @return the number of bits in this string
     */
    public int length(){
       return this.sb.length();
    }

    /**
     * Appends the bit string representation of the parameter to this bit string.
     * Each digit represents a single bit.  If any digit of the parameter is not
     * 0 or 1 the behavior is undefined.
     * @param i
     * @return a reference to this bit string
     */
    public StringOfBits append(int i) {
        this.sb.append(i);
        return sb;
    }

    /**
     * Appends the bit string representation of the parameter to this bit string.
     * Each digit represents a single bit.  If any digit of the parameter is not
     * 0 or 1 the behavior is undefined.
     * @param str - a string
     * @return a reference to this bit string
     */
    public StringOfBits append(CharSequence str){
       this.sb.append(str);
       return sb;
    }
    /**
     * Appends the paramter to this bit string
     * @param bitstr - a string
     * @return a reference to this bit string
     */
    public StringOfBits append(StringOfBits bitstr){
        return this.sb.append(bitstr);
    }

    /**
     * Returns a char corresponding to the bit at the specified index.
     * @param index - the index of the desired bit value
     * @return the char value at the specified index
     * @throws IndexOutOfBoundsException - if index is negative or greater
     * than or equal to length
     */
    public char charAt(int index) throws IndexOutOfBoundsException{
        if(index < 0 || index >= length()){
            throw new IndexOutOfBoundsException("Out Of Bounds");
        }
        return this.sb.charAt(index);
    }

    /**
     * Returns an int corresponding to the bit at the specified index.
     * @param index - the index of the desired bit value
     * @return an int value corresponding to specified index
     * @throws IndexOutOfBoundsException - if index is negative or greater
     * than or equal to length
     */

    public int intAt(int index){
        if(index < 0 || index >= length()){
            throw new IndexOutOfBoundsException("Out Of Bounds");
        }
        return this.sb.intAt(index);
    }

    /**
     * Returns a boolean corresponding to the bit at the specified index.
     * @param index - the index of the desired bit value
     * @return the boolean value at the specified index
     * @throws IndexOutOfBoundsException - if index is negative or greater
     * than or equal to length
     */
    public boolean booleanAt(int index){
        if (index < 0 || index >= length()){
            throw new IndexOutOfBoundsException("Out Of Bounds");
        }
        if (this.sb.charAt(index) == 0) {
            return true;
        }
        else if (this.sb.charAt(index) == 1) {
            return false;
         }
        else {
            return false;
        }

    }

    /**
     * Sets the bit at the specified index.  If the parameter is not '0' or '1'
     * the behavior of this method is undefined
     * @param index - the index of the bit to modify
     * @param c - the new value
     */

    public void setBitAt(int index, char c){

    }

    /**
     * Sets the bit at the specified index.  If the parameter is not '0' or '1'
     * the behavior of this method is undefined
     * @param index - the index of the bit to modify
     * @param i  - the new value
     */

    public void setBitAt(int index, int i){

    }

    /**
     * Sets the bit at the specified index.
     * @param index - the index of the bit to modify
     * @param b- the new value
     */

    public void setBitAt(int index, boolean b){

    }

    /**
     * Method that over rides th to string method
     */
    @Override
    public String toString(){
        return "";
    }
}