new Task059.

src/main/java/com/epam/university/java/core/task059/Task059.java

@@ -0,0 +1,19 @@
+package com.epam.university.java.core.task059;
+
+/**
+ * Count sort.
+ *
+ * <p>
+ *     Given a list of integers. Every number is > 0 and < 10.
+ *     Need to sort the sequence. Algorithm complexity must be O(n).
+ * </p>
+ */
+public interface Task059 {
+    /**
+     * Returns sorted sequence.
+     *
+     * @param sequence array to sort
+     * @return sorted array
+     */
+    int[] countSort(int[] sequence);
+}

src/test/java/com/epam/university/java/core/task059/Task059Test.java

@@ -0,0 +1,42 @@
+package com.epam.university.java.core.task059;
+
+import com.epam.university.java.core.helper.TestHelper;
+import com.epam.university.java.core.task056.Task056;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class Task059Test {
+    private Task059 instance;
+
+    @Before
+    public void setUp() throws Exception {
+        instance = TestHelper.getInstance(Task059.class);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void arrayIsNull() throws Exception {
+        instance.countSort(null);
+    }
+
+    @Test
+    public void first() throws Exception {
+        final int[] input = {1, 3, 2, 7, 2, 2, 2, 3};
+        final int[] target = {1, 2, 2, 2, 3, 3, 7};
+        final int[] actual = instance.countSort(input);
+        for (int i = 0; i < target.length; i++) {
+            assertEquals("Wrong result", target[i], actual[i]);
+        }
+    }
+
+    @Test
+    public void second() throws Exception {
+        final int[] input = {2, 1, 1, 1, 3, 2, 2, 2, 3, 2, 3, 2, 2, 1, 1};
+        final int[] target = {1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3};
+        final int[] actual = instance.countSort(input);
+        for (int i = 0; i < target.length; i++) {
+            assertEquals("Wrong result", target[i], actual[i]);
+        }
+    }
+}