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Added [FEATURE REQUEST] Golden Ration formula to find Nth Fibonacci number TheAlgorithms#4505 (TheAlgorithms#4513)
* Create FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Create FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumber.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update FibonacciNumber.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciNumber.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Delete src/main/java/com/thealgorithms/maths/FibonacciNumberTest.java * Create FibonacciNumberTest.java * Update FibonacciNumber.java * Update FibonacciNumberTest.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumberTest.java * Update src/test/java/com/thealgorithms/maths/FibonacciNumberTest.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Create FibonacciCalculator.java * Update FibonacciNumberTest.java * Update and rename FibonacciCalculator.java to FibCalc.java * Update FibonacciNumberTest.java * Update FibCalc.java * Update FibonacciNumber.java * Delete src/test/java/com/thealgorithms/maths/FibCalc.java * Create FibCalc.java * Update FibonacciNumberTest.java * Update FibCalc.java * Update FibonacciNumberTest.java * Update FibonacciNumber.java * Update FibonacciNumberTest.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumber.java * Update FibonacciNumberTest.java * Update FibonacciNumber.java * fix: use proper name * fix: use proper class name * tests: add `returnsCorrectValues` * Update and rename FibCalc.java to Fibonacci.java * Update Fibonacci.java * Update FibonacciNumber.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update Fibonacci.java * Update FibonacciNumber.java * Update and rename FibCalcTest.java to FibonacciTest.java * Update FibonacciNumber.java * Update Fibonacci.java * Update Fibonacci.java * Update Fibonacci.java * Update FibonacciTest.java * Update Fibonacci.java * Update src/main/java/com/thealgorithms/maths/Fibonacci.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/test/java/com/thealgorithms/maths/FibonacciNumberTest.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/test/java/com/thealgorithms/maths/FibonacciNumberTest.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update FibonacciTest.java * Update FibonacciNumberTest.java * Update FibonacciNumberTest.java * Update FibonacciTest.java * Update src/main/java/com/thealgorithms/maths/Fibonacci.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/test/java/com/thealgorithms/maths/FibonacciNumberTest.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/test/java/com/thealgorithms/maths/FibonacciTest.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/Fibonacci.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/main/java/com/thealgorithms/maths/FibonacciNumber.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/test/java/com/thealgorithms/maths/FibonacciNumberTest.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/test/java/com/thealgorithms/maths/FibonacciNumberTest.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update src/test/java/com/thealgorithms/maths/FibonacciNumberTest.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update FibonacciNumber.java * Update FibonacciNumber.java * Update Fibonacci.java * Update FibonacciNumber.java * Update and rename FibonacciNumber.java to FibonacciNumberGoldenRation.java * Update and rename FibonacciNumberTest.java to FibonacciNumberGoldenRationTest.java * Update Fibonacci.java * Update FibonacciNumberGoldenRation.java * Update FibonacciNumberGoldenRationTest.java * Update FibonacciTest.java * Update Fibonacci.java * Update FibonacciNumberGoldenRationTest.java * Update FibonacciNumberGoldenRationTest.java * Update FibonacciNumberGoldenRation.java * Update FibonacciNumberGoldenRation.java * Update FibonacciNumberGoldenRationTest.java * Update FibonacciNumberGoldenRationTest.java * Update src/main/java/com/thealgorithms/maths/FibonacciNumberGoldenRation.java Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> * Update and rename Fibonacci.java to FibonacciLoop.java * Update FibonacciNumberGoldenRation.java * Update FibonacciNumberGoldenRationTest.java * Update and rename FibonacciTest.java to FibonacciLoopTest.java * Update FibonacciLoop.java * Update FibonacciLoop.java * Update FibonacciNumberGoldenRation.java * docs: add missing dot --------- Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com> Co-authored-by: vil02 <vil02@o2.pl>
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‎src/main/java/com/thealgorithms/maths/FibonacciLoop.java

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package com.thealgorithms.maths;
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import java.math.BigInteger;
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/**
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* This class provides methods for calculating Fibonacci numbers using BigInteger for large values of 'n'.
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*/
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public final class FibonacciLoop {
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private FibonacciLoop() {
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// Private constructor to prevent instantiation of this utility class.
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}
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/**
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* Calculates the nth Fibonacci number.
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*
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* @param n The index of the Fibonacci number to calculate.
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* @return The nth Fibonacci number as a BigInteger.
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* @throws IllegalArgumentException if the input 'n' is a negative integer.
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*/
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public static BigInteger compute(final int n) {
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if (n < 0) {
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throw new IllegalArgumentException("Input 'n' must be a non-negative integer.");
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}
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if (n <= 1) {
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return BigInteger.valueOf(n);
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}
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BigInteger prev = BigInteger.ZERO;
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BigInteger current = BigInteger.ONE;
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for (int i = 2; i <= n; i++) {
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BigInteger next = prev.add(current);
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prev = current;
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current = next;
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}
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return current;
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}
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}

‎src/main/java/com/thealgorithms/maths/FibonacciNumberGoldenRation.java

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package com.thealgorithms.maths;
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/**
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* This class provides methods for calculating Fibonacci numbers using Binet's formula.
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* Binet's formula is based on the golden ratio and allows computing Fibonacci numbers efficiently.
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*
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* @see <a href="https://en.wikipedia.org/wiki/Fibonacci_sequence#Binet's_formula">Binet's formula on Wikipedia</a>
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*/
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public final class FibonacciNumberGoldenRation {
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private FibonacciNumberGoldenRation() {
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// Private constructor to prevent instantiation of this utility class.
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}
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/**
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* Compute the limit for 'n' that fits in a long data type.
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* Reducing the limit to 70 due to potential floating-point arithmetic errors
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* that may result in incorrect results for larger inputs.
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*/
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public static final int MAX_ARG = 70;
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/**
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* Calculates the nth Fibonacci number using Binet's formula.
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*
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* @param n The index of the Fibonacci number to calculate.
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* @return The nth Fibonacci number as a long.
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* @throws IllegalArgumentException if the input 'n' is negative or exceeds the range of a long data type.
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*/
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public static long compute(int n) {
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if (n < 0) {
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throw new IllegalArgumentException("Input 'n' must be a non-negative integer.");
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}
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if (n > MAX_ARG) {
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throw new IllegalArgumentException("Input 'n' is too big to give accurate result.");
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}
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if (n <= 1) {
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return n;
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}
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// Calculate the nth Fibonacci number using the golden ratio formula
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final double sqrt5 = Math.sqrt(5);
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final double phi = (1 + sqrt5) / 2;
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final double psi = (1 - sqrt5) / 2;
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final double result = (Math.pow(phi, n) - Math.pow(psi, n)) / sqrt5;
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// Round to the nearest integer and return as a long
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return Math.round(result);
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}
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}

‎src/test/java/com/thealgorithms/maths/FibonacciLoopTest.java

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package com.thealgorithms.maths;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import java.math.BigInteger;
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import org.junit.jupiter.api.Test;
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public class FibonacciLoopTest {
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@Test
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public void checkValueAtZero() {
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assertEquals(BigInteger.ZERO, FibonacciLoop.compute(0));
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}
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@Test
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public void checkValueAtOne() {
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assertEquals(BigInteger.ONE, FibonacciLoop.compute(1));
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}
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@Test
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public void checkValueAtTwo() {
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assertEquals(BigInteger.ONE, FibonacciLoop.compute(2));
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}
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@Test
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public void checkRecurrenceRelation() {
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for (int i = 0; i < 100; ++i) {
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assertEquals(FibonacciLoop.compute(i + 2), FibonacciLoop.compute(i + 1).add(FibonacciLoop.compute(i)));
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}
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}
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@Test
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public void checkNegativeInput() {
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assertThrows(IllegalArgumentException.class, () -> { FibonacciLoop.compute(-1); });
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}
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}

‎src/test/java/com/thealgorithms/maths/FibonacciNumberGoldenRationTest.java

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package com.thealgorithms.maths;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import java.math.BigInteger;
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import org.junit.jupiter.api.Test;
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public class FibonacciNumberGoldenRationTest {
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@Test
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public void returnsCorrectValues() {
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for (int n = 0; n <= FibonacciNumberGoldenRation.MAX_ARG; ++n) {
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final var actual = FibonacciNumberGoldenRation.compute(n);
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final var expected = FibonacciLoop.compute(n);
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assertEquals(expected, BigInteger.valueOf(actual));
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}
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}
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@Test
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public void throwsIllegalArgumentExceptionForNegativeInput() {
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assertThrows(IllegalArgumentException.class, () -> { FibonacciNumberGoldenRation.compute(-1); });
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}
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@Test
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public void throwsIllegalArgumentExceptionForLargeInput() {
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assertThrows(IllegalArgumentException.class, () -> { FibonacciNumberGoldenRation.compute(FibonacciNumberGoldenRation.MAX_ARG + 1); });
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}
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}

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