The program should perform the operation and print the resulting set

lOMoARcPSD|16107334

In mathematics, several operations are de�ned on sets. The union of two sets A and B is a set that contains all the elements that are in A together with all the elements that are in B. The intersection of A and B is the set that contains elements that are in both A and B. The di�erence of A and B is the set that contains all the elements of A except for those elements that are also in B.

Suppose that A and B are variables of type set in Java. The mathematical operations on A and B can be computed using methods from the Set interface. In particular: A.addAll(B) computes the union of A and B; A.retainAll(B) computes the intersection of A and B; and A.removeAll(B) computes the di�erence of A and B.

		/
		/

lOMoARcPSD|16107334

[1, 2, 3] + [3, 5, 7] [ 1, 2, 3, 5, 7]
[10,9,8,7] * [2,4,6,8] [8]
[ 5, 10, 15, 20 ] - [ 0, 10, 20 ] [5, 15]

Start with an empty set.

Read the '[' that begins the set.

lOMoARcPSD|16107334

Return the set.

Read the operator.

Read the second set, B.

In the program, an error check has to be added to make sure that there is a legal operator in the correct position. I also add an error check to make sure that there is no extra data on the line.

The Solution
import java.util.TreeSet;

* The program ends when the user inputs an empty line.

*
* This program is mainly a demonstration of Sets.

while (true) {
char ch;
System.out.print("\n? ");
TextIO.skipBlanks();
if (TextIO.peek() == '\n') {
// The input line is empty.

// Exit the loop and end the program.

} // end main()

A = readSet(); // Read the �rst set.

TextIO.skipBlanks();
if (TextIO.peek() != '*' && TextIO.peek() != '+'
&& TextIO.peek() != '-')
throw new IllegalArgumentException(
"Expected *, +, or - after �rst set.");
op = TextIO.getAnyChar(); // Read the operator.

else if (op == '*')
A.retainAll(B); // Intersection.

else
A.removeAll(B); // Set di�erence.

lOMoARcPSD|16107334

* and stores them in a TreeSet that contains objects belonging
* to the wrapper class Integer. The set must be enclosed
* between square brackets and must contain a list of zero or
* more non-negative integers, separated by commas. Spaces
* are allowed anywhere. If the input is not of the correct
* form, an IllegalArgumentException is thrown.

TextIO.getAnyChar(); // Read the ']'.

return set;
}

else
throw new IllegalArgumentException("Expected ',' or ']'.");
}

TextIO.getAnyChar(); // Read the ']' that ended the set.

	/

Last modi�ed: Wednesday, 13 May 2020, 3:51 PM