diff --git a/src/IntListTest.java b/src/IntListTest.java
new file mode 100644
index 0000000..98363b9
--- /dev/null
+++ b/src/IntListTest.java
@@ -0,0 +1,92 @@
+import java.util.ArrayList;
+import java.util.Scanner;
+
+public class IntListTest {
+
+    public static void main(String[] args) {
+        new IntListTest();
+    }
+
+    Scanner scan;
+
+    IntListTest() {
+        scan = new Scanner(System.in);
+        AvgIL intlist = new AvgIL();
+        System.out.println("Input integer or n|sum|avg|list|exit");
+        while (true) {
+            String in = scan.next();
+            if (in.equals("exit")) {
+                System.exit(0);
+            } else if (in.equals("list")) {
+                intlist.show();
+            } else if (in.equals("n")) {
+                System.out.println("n=" + intlist.size());
+            } else if (in.equals("sum")) {
+                System.out.println("sum=" + intlist.getSum());
+            } else if (in.equals("avg")) {
+                System.out.println("avg=" + intlist.getAvg());
+            } else if (in.matches("[0-9]+")) { // Int value
+                int num = Integer.parseInt(in);
+                intlist.add(num);
+                // System.out.println("sum="+intlist.getSum()+" avg="+intlist.getAvg()+"
+                // n="+intlist.size());
+            }
+        }
+    }
+}
+
+class IntList {
+    protected ArrayList<Integer> intlist; // storage of int values
+
+    IntList() {
+        intlist = new ArrayList<Integer>();
+    }
+
+    public void add(int n) {
+        intlist.add(n);
+    }
+
+    public int size() {
+        return intlist.size();
+    }
+
+    public void show() {
+        for (int k : intlist) {
+            System.out.print(k + " ");
+        }
+        System.out.println("");
+    }
+}
+
+class SumIL extends IntList {
+    private float sum = 0;
+
+    public void add(int n) {
+        super.add(n);
+        // update sum
+        sum = 0;
+        for (int k : intlist) {
+            sum += k;
+        }
+    }
+
+    public float getSum() {
+        return sum;
+    }
+}
+
+class AvgIL extends SumIL {
+    private float avg = 0;
+
+    public void add(int n) {
+        super.add(n);
+        // update avg
+        float s = getSum();
+        System.out.println("sum="+s);
+        avg = -99999;
+    }
+
+    public float getAvg() {
+        return avg;
+    }
+}
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