TheAlgorithms/Java · error · IllegalArgumentException

Denominator cannot be 0

Error message

Denominator cannot be 0

What it means

ADTFraction is a Java record representing a fraction; its compact constructor rejects denominator == 0 because division by zero is undefined. Since records validate in the constructor, any creation of an ADTFraction with denominator 0 throws — including internal calls from plus(), times(), and reciprocal() if those produce a zero denominator.

Source

Thrown at src/main/java/com/thealgorithms/maths/ADTFraction.java:13

package com.thealgorithms.maths;

public record ADTFraction(int numerator, int denominator) {
    /**
     * Initializes a newly created {@code ADTFraction} object so that it represents
     * a fraction with the {@code numerator} and {@code denominator} provided as arguments.
     *
     * @param numerator   The fraction numerator
     * @param denominator The fraction denominator
     */
    public ADTFraction {
        if (denominator == 0) {
            throw new IllegalArgumentException("Denominator cannot be 0");
        }
    }

    /**
     * Add two fractions.
     *
     * @param fraction the {@code ADTFraction} to add
     * @return A new {@code ADTFraction} containing the result of the operation
     */
    public ADTFraction plus(ADTFraction fraction) {
        var numerator = this.denominator * fraction.numerator + this.numerator * fraction.denominator;
        var denominator = this.denominator * fraction.denominator;
        return new ADTFraction(numerator, denominator);
    }

    /**
     * Multiply fraction by a number.
     *

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Validate denominator != 0 before constructing; for reciprocal, check numerator != 0 first.
2. When taking input, reject or prompt again if the denominator is 0.
3. In arithmetic chains, guard reciprocal() callers against zero numerators.

Example fix

// before
ADTFraction f = new ADTFraction(3, 0);
ADTFraction r = someFraction.reciprocal(); // fails if someFraction.numerator()==0

// after
if (denominator == 0) throw new IllegalArgumentException("denominator must be non-zero");
ADTFraction f = new ADTFraction(3, denominator);
if (someFraction.numerator() == 0) throw new ArithmeticException("cannot invert zero fraction");
ADTFraction r = someFraction.reciprocal();

if (denominator == 0) {
    throw new IllegalArgumentException("denominator cannot be 0");
}
new ADTFraction(numerator, denominator);
// for reciprocal:
if (f.numerator() == 0) {
    throw new ArithmeticException("cannot take reciprocal of a zero fraction");
}
f.reciprocal();

When it happens

Trigger: Constructing new ADTFraction(n, 0), or calling reciprocal() on a fraction whose numerator is 0 (reciprocal swaps num/den, yielding denominator=0). Also times(0) internally constructs ADTFraction(0,1) then multiplies — safe — but a plus/times producing a zero denominator via arithmetic is theoretically possible with overflow.

Common situations: Calling reciprocal() on ADTFraction(0, 5) (zero numerator), user input with denominator 0, or a computation that yields a zero denominator through cancellation/overflow.

Related errors

• capacity must greater than 0!
• Capacity must be greater than 0!
• Capacity cannot be negative.
• initialCapacity < 1
• Numbers array cannot be empty or null

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/af021be24b47adf4. Report an issue: GitHub.