In preparation for a class Fraction, create a class NullDenominatorException that must be a checked exception whose instances are thrown if the denominator of an object of class Fraction is 0.

Sure, here's an example implementation of the NullDenominatorException class in Java:

public class NullDenominatorException extends Exception {
    public NullDenominatorException() {
        super("Denominator cannot be null or zero.");
    }
}

In this implementation, we extend the built-in Exception class to create our custom exception. We also provide a constructor that sets the exception message to a default value of "Denominator cannot be null or zero.". This message will be displayed when the exception is thrown.

To use this exception in our Fraction class, we can add a check for a null or zero denominator in the constructor and throw the exception if necessary. Here's an example implementation of the Fraction class:

public class Fraction {
    private int numerator;
    private int denominator;

    public Fraction(int numerator, int denominator) throws NullDenominatorException {
        if (denominator == 0) {
            throw new NullDenominatorException();
        }
        this.numerator = numerator;
        this.denominator = denominator;
    }

    // other methods for adding, subtracting, multiplying, and dividing Fractions
}

In this implementation, we check if the denominator is 0 and throw a NullDenominatorException if it is. Otherwise, we set the numerator and denominator instance variables and continue with the construction of the Fraction object.