How can I fix this error in my code? Give feedback public class TestUnitFraction{public static void main(String[] args){Fraction f1 = new UnitFraction(3, 3, "mile", "hour");Fraction f2 = new UnitFraction(4, 12, "mile", "hour");Fraction f3 = new UnitFraction(5, 10, "dollar", "gallon");Fraction f4 = new UnitFraction(-6, 8, "gallon", "gallon");Fraction f5 = new IntegerFraction(9, 4);Fraction f6 = new UnitFraction(6, 8, null, null);System.out.println("f1 = " + f1);System.out.println("f2 = " + f2);System.out.println("f3 = " + f3);System.out.println("f4 = " + f4);System.out.println("f1 + f2 = " + f1.add(f2));System.out.println("f3 + f4 = " + f3.add(f4));System.out.println("f2 in decimal is: " + ((UnitFraction) f2).decimalValue());System.out.println("f1 + f3 = " + f1.add(f3));System.out.println("f2 + f5 = " + f2.add(f5));System.out.println("f6 + f5 = " + f5.add(f6));}}.