How to detect outliers in an ArrayList

Question

I\'m trying to think of some code that will allow me to search through my ArrayList and detect any values outside the common range of \"good values.\"

Example: 100 1

Answer 1

I'm very glad and thanks to Valiyev. His solution helped me a lot. And I want to shere my little SRP on his works.

Please note that I use List.of() to store Dixon's critical values, for this reason it is required to use Java higher than 8.

public class DixonTest {
protected List criticalValues = 
    List.of(0.941, 0.765, 0.642, 0.56, 0.507, 0.468, 0.437);
private double scaleOfElimination;
private double mean;
private double stdDev;

private double getMean(final List input) {
    double sum = input.stream()
            .mapToDouble(value -> value)
            .sum();
    return (sum / input.size());
}

  private double getVariance(List input) {
    double mean = getMean(input);
    double temp = input.stream()
            .mapToDouble(a -> a)
            .map(a -> (a - mean) * (a - mean))
            .sum();
    return temp / (input.size() - 1);
}

private double getStdDev(List input) {
    return Math.sqrt(getVariance(input));
}

protected List eliminateOutliers(List input) {
    int N = input.size() - 3;
    scaleOfElimination = criticalValues.get(N).floatValue();
    mean = getMean(input);
    stdDev = getStdDev(input);

    return input.stream()
            .filter(this::isOutOfBounds)
            .collect(Collectors.toList());
}

private boolean isOutOfBounds(Double value) {
    return !(isLessThanLowerBound(value)
            || isGreaterThanUpperBound(value));
}

private boolean isGreaterThanUpperBound(Double value) {
    return value > mean + stdDev * scaleOfElimination;
}

private boolean isLessThanLowerBound(Double value) {
    return value < mean - stdDev * scaleOfElimination;
}
}

I hope it will help someone else.

Best regard