int[] data = {}; //data array store digits in this natural number

/**

* THIS IS A HELPER method which converses a digit character to its integer value.

* @param c is character and assumed be one of the following '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'

* @return an integer value of character in c

*/

private int toInt(char c)

{

return (int)c - (int)'0';

}

/**

* A parameterized constructor

* @param initData is a String containing the digits of this NaturalNumber

* instantiate the data array to correct size and store the digits from initData

* as an integer in array data.

*

* The constructor should use its setter to set each digit to

*/

public NaturalNumber(String initData)

{

// write code

return;

}

/**

* A setter : setting an integer between 0 to 9 to a digit specified by parameter digitIndex to the data array

* @param digitIndex is the index to data array

* @param value is an integer between 0 and 9

*

* setter validation:

* @param digitIndex must be between 0 and data.length - 1 AND @param value must be between 0 and 9

* otherwise, this setter should not do anything to the data array.

*/

public void setDigit(int digitIndex, int value)

{

//write code

return;

}

/**

* A getter : getting a digit from this NaturalNumber.

* @param digitIndex is the index to the data array.

* @return the integer value specified by @param digitIndex if digitIndex is between 0 and data.length - 1

* otherwise return -1

*/

public int getDigit(int digitIndex)

{

//write code

}

/**

* A compare method to compare this NaturalNumber to other NaturalNumber.

* @param other an instance of another NaturalNumber class to compare this NaturalNumber

* @return 0 if this and other are equal

* 1 if this is bigger than other

* -1 if this is smaller than other

*

* ALGORITHM:

* 1) Strip leading zeros from both this and other natural number

* 2) See if one is longer. If it is, it is bigger.

* 3) If not, take the leftmost digit of both numbers, and compare them. If one is bigger, then that number is bigger.

* 4) Otherwise, continue comparing digits until you reach the rightmost one. If they are the same, the numbers are the equals.

*/

public int compareTo(NaturalNumber other)

{

//write code

}

/**

*

* @return number of digits in this NaturalNumber

*/

public int numberOfDigits()

{

return data.length;

}

/**

* converse this NaturalNumber to a string

*/

public String toString()

{

String s = "";

for(int i = 0; i < numberOfDigits() ; i = i + 1)

{

s = s + (getDigit(i) + "");

}

return s;

}

}

public class Operator

{

/**

* Add two natural numbers

* @param a is a NaturalNumber

* @param b is a NaturalNumber

* @return an instance of a class NaturalNumber which is the result of adding a and b

*/

public static NaturalNumber add(NaturalNumber a, NaturalNumber b)

{

//write code

}

/**

* Subtract two natural numbers

* @param a is a NaturalNumber

* @param b is a NaturalNumber

* @return if a is larger than b, return an instance of a class NaturalNumber

* which is the result of subtracting b from a.

* otherwise return an instance of class NaturalNumber with 0

*/

public static NaturalNumber subtract(NaturalNumber a, NaturalNumber b)

{

//write code

}

}