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Task/Standard-deviation/Java/standard-deviation.java

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+import java.util.LinkedList;
+public class StdDev {
+    LinkedList<Double> nums;
+    public StdDev() {
+        nums = new LinkedList<Double>();
+    }
+    public static void main(String[] args) {
+        double[] testData = {2,4,4,4,5,5,7,9};
+        StdDev sd = new StdDev();
+
+        for (double x : testData) {
+            sd.newNum(x);
+            System.out.println(sd.getSD());
+        }
+    }
+
+    public void newNum(double num) {
+        nums.add(num);
+    }
+
+    public double getAvg() {
+        if (nums.isEmpty()) return 0;
+        double ret = 0;
+        double sum = 0;
+        for (double num : nums) {
+           sum += num;
+        }
+        return sum / nums.size();
+    }
+
+    public double getSD() {
+        double sqDiffs = 0;
+        double avg = getAvg();
+        for (double num : nums) {
+           sqDiffs += (num - avg) * (num - avg);
+        }
+        return Math.sqrt(sqDiffs / nums.size());
+    }
+}