Means.java

packagecom.thealgorithms.maths;

importjava.util.stream.StreamSupport;
importorg.apache.commons.collections4.IterableUtils;

/**
 * https://en.wikipedia.org/wiki/Mean
 * <p>
 * by: Punit Patel
 */
publicfinalclassMeans {

privateMeans() {
 }

/**
 * @brief computes the [Arithmetic Mean](https://en.wikipedia.org/wiki/Arithmetic_mean) of the input
 * @param numbers the input numbers
 * @throws IllegalArgumentException empty input
 * @return the arithmetic mean of the input numbers
 */
publicstaticDoublearithmetic(finalIterable<Double> numbers) {
checkIfNotEmpty(numbers);
returnStreamSupport.stream(numbers.spliterator(), false).reduce((x, y) -> x + y).get() / IterableUtils.size(numbers);
 }

/**
 * @brief computes the [Geometric Mean](https://en.wikipedia.org/wiki/Geometric_mean) of the input
 * @param numbers the input numbers
 * @throws IllegalArgumentException empty input
 * @return the geometric mean of the input numbers
 */
publicstaticDoublegeometric(finalIterable<Double> numbers) {
checkIfNotEmpty(numbers);
returnMath.pow(StreamSupport.stream(numbers.spliterator(), false).reduce((x, y) -> x * y).get(), 1d / IterableUtils.size(numbers));
 }

/**
 * @brief computes the [Harmonic Mean](https://en.wikipedia.org/wiki/Harmonic_mean) of the input
 * @param numbers the input numbers
 * @throws IllegalArgumentException empty input
 * @return the harmonic mean of the input numbers
 */
publicstaticDoubleharmonic(finalIterable<Double> numbers) {
checkIfNotEmpty(numbers);
returnIterableUtils.size(numbers) / StreamSupport.stream(numbers.spliterator(), false).reduce(0d, (x, y) -> x + 1d / y);
 }

privatestaticvoidcheckIfNotEmpty(finalIterable<Double> numbers) {
if (!numbers.iterator().hasNext()) {
thrownewIllegalArgumentException("Emtpy list given for Mean computation.");
 }
 }
}