Question

Using Java programming language, build a class called IntegerSet.

Instructions

- Create class IntegerSet

• An IntegerSet object holds integers in the range 0-100
• Represented by an array of booleans, such that array element a[i] is set to true if integer i is in the set, and false otherwise
• Create these constructors and methods for the class

    IntegerSet()
    public IntegerSet union(IntegerSet iSet)
    public IntegerSet intersection(IntegerSet iSet)
    public IntegerSet insertElement(int data)
    public IntegerSet deleteElement(int data)
    public boolean isEqualTo(IntegerSet iSet)
    public String toString()
  

• The constructor (no arguments) initializes the array to represent the "empty set" (i.e. no integers in the set)
• Method union creates and returns a new set that is the set-theoretic union of the two existing sets (the calling object and the parameter). An element is in the union if it's in either of the starting two sets
• Method intersection creates and returns a new set that is the set-theoretic intersection of the two existing sets (the calling object and the parameter). An element is in the intersection if it's in BOTH of the starting two sets
• Method insertElement adds the argument (an integer) to the set (the calling object), and also should return that set (so that calls can be cascaded)
• Method deleteElement removes the argument (an integer) from the set (the calling object), and also should return that set (so that calls can be cascaded)
• Method isEqualTo determines whether two sets are equal (i.e. they have all the same elements), returning a true or false indication
• Method toString returns a string containing the set elements as a list of numbers, in ascending order, separated by spaces. Include only elements present in the set. Use "---" to represent an empty set.

Here's the sample run:

After set1.insertElement(10), set1 = 0 2 8 10
default IntegerSet is = ---
set1 = 0 2 4 6 8 10 12 95 100
set2 = 0 3 6 9 12
set1.union(set2) = 0 2 3 4 6 8 9 10 12 95 100
set1.intersection(set2) = 0 6 12
set1.deleteElement(2) = 0 4 6 8 10 12 95 100
set1.isEqualTo(set1) = true
set1.isEqualTo(set2) = false

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

//IntegerSet.java

public class IntegerSet {

    // array of booleans

    private boolean set[];

    // constructor

    public IntegerSet() {

        // initializing array of capacity 101, so that it can store values from

        // 0-100 as booleans

        set = new boolean[101];

    }

    // creates and returns a new set that is the set-theoretic union of the two

    // existing sets (the calling object and the parameter). An element is in

    // the union if it's in either of the starting two sets

    public IntegerSet union(IntegerSet iSet) {

        // creating a resultant set

        IntegerSet result = new IntegerSet();

        // looping through each index in boolean array

        for (int i = 0; i < set.length; i++) {

             // setting set[i] of result set to true if it is true in either

             // this.set[i] OR iSet.set[i]

             if (set[i] || iSet.set[i]) {

                 result.set[i] = true;

             }

        }

        return result;

    }

    // creates and returns a new set that is the set-theoretic intersection of

    // the two existing sets (the calling object and the parameter)

    public IntegerSet intersection(IntegerSet iSet) {

        // creating a resultant set

        IntegerSet result = new IntegerSet();

        for (int i = 0; i < set.length; i++) {

             // setting set[i] of result set to true if it is true in BOTH

             // this.set[i] AND iSet.set[i]

            if (set[i] && iSet.set[i]) {

                 result.set[i] = true;

             }

        }

        return result;

    }

    // adds the argument (an integer) to the set (the calling object), and also

    // should return that set (so that calls can be cascaded)

    public IntegerSet insertElement(int data) {

        // validating the range of data before setting set[data] to true

        if (data >= 0 && data < set.length) {

             set[data] = true;

        }

        return this;

    }

    // removes the argument (an integer) from the set (the calling object), and

    // also should return that set (so that calls can be cascaded)

    public IntegerSet deleteElement(int data) {

        // validating the range of data before setting set[data] to false

        if (data >= 0 && data < set.length) {

             set[data] = false;

        }

        return this;

    }

    // determines whether two sets are equal (i.e. they have all the same

    // elements)

    public boolean isEqualTo(IntegerSet iSet) {

        for (int i = 0; i < set.length; i++) {

             if (this.set[i] != iSet.set[i]) {

                 // mismatch found

                 return false;

             }

        }

        // equal

        return true;

    }

    // returns a string containing the set elements as a list of numbers, in

    // ascending order

    public String toString() {

        String str = "";

        // appending index values of set, in which the value is true, to str

        for (int i = 0; i < set.length; i++) {

             if (set[i]) {

                 str += i + " ";

             }

        }

        // if str is still blank, returning "---" indicating empty

        if (str.equals("")) {

             return "---";

        } else {

             // otherwise returning str after stripping last stray white space

             return str.trim();

        }

    }

    // main method for testing

    public static void main(String[] args) {

        // creating two sets, demonstrating different methods

        IntegerSet set1 = new IntegerSet();

        set1.insertElement(1);

        set1.insertElement(3);

        set1.insertElement(4);

        set1.insertElement(7);

        IntegerSet set2 = new IntegerSet();

        set2.insertElement(2);

        set2.insertElement(3);

        set2.insertElement(4);

        set2.insertElement(8);

        set2.insertElement(9);

        System.out.println("set1: " + set1);

        System.out.println("set2: " + set2);

        System.out.println("set1 union set2: " + set1.union(set2));

        System.out

                 .println("set1 intersection set2: " + set1.intersection(set2));

        System.out.println("set1 is equal to set2: " + set1.isEqualTo(set2));

        System.out.println("set1 delete element 1: " + set1.deleteElement(1));

        System.out.println("set1 delete element 7: " + set1.deleteElement(7));

        System.out.println("set2 delete element 2: " + set2.deleteElement(2));

        System.out.println("set2 delete element 9: " + set2.deleteElement(9));

        System.out.println("set2 delete element 8: " + set2.deleteElement(8));

        System.out.println("set1 is equal to set2: " + set1.isEqualTo(set2));

    }

}

/*OUTPUT*/

set1: 1 3 4 7

set2: 2 3 4 8 9

set1 union set2: 1 2 3 4 7 8 9

set1 intersection set2: 3 4

set1 is equal to set2: false

set1 delete element 1: 3 4 7

set1 delete element 7: 3 4

set2 delete element 2: 3 4 8 9

set2 delete element 9: 3 4 8

set2 delete element 8: 3 4

set1 is equal to set2: true