1 files changed, 110 insertions, 0 deletions
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/Stats.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/Stats.java
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index 0000000000..efa6e7ddc3
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+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/Stats.java
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2019, Matthias Sohn <matthias.sohn@sap.com> and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+package org.eclipse.jgit.util;
+
+/**
+ * Simple double statistics, computed incrementally, variance and standard
+ * deviation using Welford's online algorithm, see
+ * https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_online_algorithm
+ *
+ * @since 5.1.9
+ */
+public class Stats {
+	private int n = 0;
+
+	private double avg = 0.0;
+
+	private double min = 0.0;
+
+	private double max = 0.0;
+
+	private double sum = 0.0;
+
+	/**
+	 * Add a value
+	 *
+	 * @param x
+	 *            value
+	 */
+	public void add(double x) {
+		n++;
+		min = n == 1 ? x : Math.min(min, x);
+		max = n == 1 ? x : Math.max(max, x);
+		double d = x - avg;
+		avg += d / n;
+		sum += d * d * (n - 1) / n;
+	}
+
+	/**
+	 * Returns the number of added values
+	 *
+	 * @return  the number of added values
+	 */
+	public int count() {
+		return n;
+	}
+
+	/**
+	 * Returns the smallest value added
+	 *
+	 * @return the smallest value added
+	 */
+	public double min() {
+		if (n < 1) {
+			return Double.NaN;
+		}
+		return min;
+	}
+
+	/**
+	 * Returns the biggest value added
+	 *
+	 * @return the biggest value added
+	 */
+	public double max() {
+		if (n < 1) {
+			return Double.NaN;
+		}
+		return max;
+	}
+
+	/**
+	 * Returns the average of the added values
+	 *
+	 * @return the average of the added values
+	 */
+	public double avg() {
+		if (n < 1) {
+			return Double.NaN;
+		}
+		return avg;
+	}
+
+	/**
+	 * Returns the variance of the added values
+	 *
+	 * @return the variance of the added values
+	 */
+	public double var() {
+		if (n < 2) {
+			return Double.NaN;
+		}
+		return sum / (n - 1);
+	}
+
+	/**
+	 * Returns the standard deviation of the added values
+	 *
+	 * @return the standard deviation of the added values
+	 */
+	public double stddev() {
+		return Math.sqrt(this.var());
+	}
+}