I need help with this CSC 220 Data Structures assignment. /*************************************************************************************  *  * This class represents a fraction whose numerator and denominator are integers.  *  * Requirements:  * 1. Implement interfaces: SimpleFractionInterface and Comparable (i.e. compareTo())  * 2. Implement methods equals() and toString() from class Object  * 3. Must work for both positive and negative fractions  * 4. Must not reduce fraction to lowest term unless simplifySimpleFraction() is invoked  * 5. Must not reduce fraction to lowest term for operations add(), subtract(), multiply() and divide()  * 6. For input 3/-10 & -3/-10, must convert them to -3/10 & 3/10 respectively (see Hint 2. below)  * 7. Must display negative fraction as -x/y,  * example: (-3)/10 or 3/(-10), must display as -3/10  * 8. Must throw only SimpleFractionException in case of errors  * 9. Must not add new or modify existing data fields  * 10.Must not add new public methods  * 11.May add private methods  *  * Hints:  *  * 1. To reduce a fraction such as 4/8 to lowest terms, you need to divide both  * the numerator and the denominator by their greatest common denominator.  * The greatest common denominator of 4 and 8 is 4, so when you divide  * the numerator and denominator of 4/8 by 4, you get the fraction 1/2.  * The recursive algorithm which finds the greatest common denominator of  * two positive integers is implemnted (see code)  *  * 2. It will be easier to determine the correct sign of a fraction if you force  * the fraction's denominator to be positive. However, your implementation must  * handle negative denominators that the client might provide.  *  * 3. You need to downcast reference parameter SimpleFractionInterface to SimpleFraction if  * you want to use it as SimpleFraction. See add, subtract, multiply and divide methods  *  * 4. Use "this" to access this object if it is needed  *  ************************************************************************************/  package PJ1; public class SimpleFraction implements SimpleFractionInterface, Comparable { // integer numerator and denominator private int num; private int den; public SimpleFraction() { // implement this method! // set fraction to default = 0/1 } // end default constructor public SimpleFraction(int num, int den) { // implement this method! } // end constructor public void setSimpleFraction(int num, int den) { // implement this method! // return SimpleFractionException if initialDenominator is 0 } // end setSimpleFraction public SimpleFractionInterface simplifySimpleFraction() { // implement this method! // return this fraction return null; } public double toDouble() { // return double floating point value // implement this method! return 0.0; } // end toDouble public SimpleFractionInterface add(SimpleFractionInterface secondFraction) { // implement this method! // use formula: a/b + c/d is (ad + cb)/(bd) // Note: do not reduce the result return null; } // end add public SimpleFractionInterface subtract(SimpleFractionInterface secondFraction) { // implement this method! // use formula: a/b - c/d is (ad - cb)/(bd) // Note: do not reduce the result return null; } // end subtract public SimpleFractionInterface multiply(SimpleFractionInterface secondFraction) { // implement this method! // use formula: a/b * c/d is (ac)/(bd) // Note: do not reduce the result return null; } // end multiply public SimpleFractionInterface divide(SimpleFractionInterface secondFraction) { // implement this method! // return SimpleFractionException if secondFraction is 0 // use formula: a/b / c/d is (ad)/(bc) // Note: do not reduce the result return null; } // end divide public boolean equals(Object other) { // implement this method! return false; } // end equals public int compareTo(SimpleFraction other) { // implement this method! return 0; } // end compareTo public String toString() { return num + "/" + den; } // end toString //----------------------------------------------------------------- // private methods start here //----------------------------------------------------------------- /** Task: Reduces a fraction to lowest terms. */  private void reduceSimpleFractionToLowestTerms() { // implement this method! // // Outline: // compute GCD of num & den // GCD works for + numbers. // So, you should eliminate - sign // then reduce numbers : num/GCD and den/GCD } // end reduceSimpleFractionToLowestTerms /** Task: Computes the greatest common divisor of two integers.  * @param integerOne an integer  * @param integerTwo another integer  * @return the greatest common divisor of the two integers */  private int GCD(int integerOne, int integerTwo) { int result; if (integerOne % integerTwo == 0) result = integerTwo; else result = GCD(integerTwo, integerOne % integerTwo); return result; } // end GCD //----------------------------------------------------------------- // Some tests are provided here // Make sure your results are same as expected results public static void main(String[] args) { SimpleFractionInterface firstOperand = null; SimpleFractionInterface secondOperand = null; SimpleFractionInterface result = null; double doubleResult = 0.0; System.out.println(" ========================================= "); firstOperand = new SimpleFraction(-12, -20); System.out.println("Input numerator & denominator: -12 & -20"); System.out.println("Result Fraction:\t\t" + firstOperand); System.out.println("\tExpected result :\t12/20 "); firstOperand.simplifySimpleFraction(); System.out.println(" After simplifySimpleFraction():" + firstOperand); System.out.println("\tExpected result :\t3/5 "); System.out.println(" ========================================= "); firstOperand = new SimpleFraction(20, -40); System.out.println("Input numerator & denominator: 20 & -40"); System.out.println("Result Fraction:\t\t" + firstOperand); System.out.println("\tExpected result :\t-20/40 "); firstOperand.simplifySimpleFraction(); System.out.println(" After simplifySimpleFraction():" + firstOperand); System.out.println("\tExpected result :\t-1/2 "); SimpleFraction nineSixteenths = new SimpleFraction(9, 16); // 9/16 SimpleFraction oneFourth = new SimpleFraction(1, 4); // 1/4 System.out.println(" ========================================= "); // 7/8 + 9/16 firstOperand = new SimpleFraction(7, 8); result = firstOperand.add(nineSixteenths); System.out.println("The sum of " + firstOperand + " and " + nineSixteenths + " is \t\t" + result); System.out.println("\tExpected result :\t\t184/128 "); if (result != null) { System.out.println(" After simplifySimpleFraction():" + result.simplifySimpleFraction()); System.out.println("\tExpected result :\t\t23/16 "); } System.out.println(" ========================================= "); // 9/16 - 7/8 firstOperand = nineSixteenths; secondOperand = new SimpleFraction(7, 8); result = firstOperand.subtract(secondOperand); System.out.println("The difference of " + firstOperand + " and " + secondOperand + " is \t" + result); System.out.println("\tExpected result :\t\t-40/128 "); System.out.println(" ========================================= "); // 15/-2 * 1/4 firstOperand = new SimpleFraction(15, -2); result = firstOperand.multiply(oneFourth); System.out.println("The product of " + firstOperand + " and " + oneFourth + " is \t" + result); System.out.println("\tExpected result :\t\t-15/8 "); System.out.println(" ========================================= "); // (-21/2) / (3/7) firstOperand = new SimpleFraction(-21, 2); secondOperand= new SimpleFraction(3, 7); result = firstOperand.divide(secondOperand); System.out.println("The quotient of " + firstOperand + " and " + secondOperand + " is \t" + result); System.out.println("\tExpected result :\t\t-147/6 "); System.out.println(" ========================================= "); // -21/2 + 7/8 firstOperand = new SimpleFraction(-21, 2); secondOperand= new SimpleFraction(7, 8); result = firstOperand.add(secondOperand); System.out.println("The sum of " + firstOperand + " and " + secondOperand + " is \t\t" + result); System.out.println("\tExpected result :\t\t-154/16 "); if (result != null) { System.out.println(" After simplifySimpleFraction():" + result.simplifySimpleFraction()); System.out.println("\tExpected result :\t\t-77/8 "); } System.out.println(" ========================================= "); // 0/10, 5/(-15), (-22)/7 firstOperand = new SimpleFraction(0, 10); doubleResult = firstOperand.toDouble(); System.out.println("The double floating point value of " + firstOperand + " is \t" + doubleResult); System.out.println("\tExpected result \t\t\t0.0 "); firstOperand = new SimpleFraction(1, -3); doubleResult = firstOperand.toDouble(); System.out.println("The double floating point value of " + firstOperand + " is \t" + doubleResult); System.out.println("\tExpected result \t\t\t-0.333333333... "); firstOperand = new SimpleFraction(-22, 7); doubleResult = firstOperand.toDouble(); System.out.println("The double floating point value of " + firstOperand + " is \t" + doubleResult); System.out.println("\tExpected result \t\t\t-3.142857142857143"); System.out.println(" ========================================= "); firstOperand = new SimpleFraction(-21, 2); System.out.println("First = " + firstOperand); // equality check System.out.println("check First equals First: "); if (firstOperand.equals(firstOperand)) System.out.println("Identity of fractions OK"); else System.out.println("ERROR in identity of fractions"); secondOperand = new SimpleFraction(-42, 4); System.out.println(" Second = " + secondOperand); System.out.println("check First equals Second: "); if (firstOperand.equals(secondOperand)) System.out.println("Equality of fractions OK"); else System.out.println("ERROR in equality of fractions"); // comparison check SimpleFraction first = (SimpleFraction)firstOperand; SimpleFraction second = (SimpleFraction)secondOperand; System.out.println(" check First compareTo Second: "); if (first.compareTo(second) == 0) System.out.println("SimpleFractions == operator OK"); else System.out.println("ERROR in fractions == operator"); second = new SimpleFraction(7, 8); System.out.println(" Second = " + second); System.out.println("check First compareTo Second: "); if (first.compareTo(second) < 0) System.out.println("SimpleFractions < operator OK"); else System.out.println("ERROR in fractions < operator"); System.out.println(" check Second compareTo First: "); if (second.compareTo(first) > 0) System.out.println("SimpleFractions > operator OK"); else System.out.println("ERROR in fractions > operator"); System.out.println(" ========================================="); System.out.println(" check SimpleFractionException: 1/0"); try { SimpleFraction a1 = new SimpleFraction(1, 0); System.out.println("Error! No SimpleFractionException"); } catch ( SimpleFractionException fe ) { System.err.printf( "Exception: %s ", fe ); } // end catch System.out.println("Expected result : SimpleFractionException! "); System.out.println(" check SimpleFractionException: division"); try { SimpleFraction a2 = new SimpleFraction(); SimpleFraction a3 = new SimpleFraction(1, 2); a3.divide(a2); System.out.println("Error! No SimpleFractionException"); } catch ( SimpleFractionException fe ) { System.err.printf( "Exception: %s ", fe ); } // end catch System.out.println("Expected result : SimpleFractionException! "); } // end main } // end SimpleFraction