Given this contract for the method swapNN: 1 2 3 4 5 6 7 8 9 10 11 12 /** * Swap

Question

Given this contract for the method swapNN:

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/**

* Swaps the two given {@code NaturalNumber}s.

*

* @param n1

*            the first {@code NaturalNumber}

* @param n2

*            the second {@code NaturalNumber}

* @updates n1

* @updates n2

* @ensures n1 = #n2 and n2 = #n1

*/

private static void swapNN(NaturalNumber n1, NaturalNumber n2) {...}

Implement the swapNN method using copyFrom (and not transferFrom).

Provide a second implementation for the swapNN method specified above using transferFrom (and not copyFrom)

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/**

* Swaps the two given {@code NaturalNumber}s.

*

* @param n1

*            the first {@code NaturalNumber}

* @param n2

*            the second {@code NaturalNumber}

* @updates n1

* @updates n2

* @ensures n1 = #n2 and n2 = #n1

*/

private static void swapNN(NaturalNumber n1, NaturalNumber n2) {...}

Explanation / Answer

import components.naturalnumber.NaturalNumber;

public class Main {
/**
* Swaps the two given {@code NaturalNumber}s.
*
* @param n1
* the first {@code NaturalNumber}
* @param n2
* the second {@code NaturalNumber}
* @updates n1
* @updates n2
* @ensures n1 = #n2 and n2 = #n1
*/
private static void swapNN(NaturalNumber n1, NaturalNumber n2) {
NaturalNumber temp = n1;
n2.copyFrom(n1);
n1.copyFrom(temp);
}

/**
* Swaps the two given {@code NaturalNumber}s.
*
* @param n1
* the first {@code NaturalNumber}
* @param n2
* the second {@code NaturalNumber}
* @updates n1
* @updates n2
* @ensures n1 = #n2 and n2 = #n1
*/
private static void swapNN2(NaturalNumber n1, NaturalNumber n2) {
NaturalNumber temp = n1;
n2.transferFrom(n1);
n1.transferFrom(temp);
}

/**
* Squares a given {@code NaturalNumber}.
*
* @param n
* the number to square
* @updates n
* @ensures n = #n * #n
*/
private static void square(NaturalNumber n) {
n.multiply(n);
}
}

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