Add 'Sets' utility class and unit tests (at request of Simon).

cougar-framework/cougar-util/src/main/java/com/betfair/cougar/util/configuration/Sets.java

@@ -0,0 +1,38 @@
+package com.betfair.cougar.util.configuration;
+
+import java.util.*;
+
+public class Sets {
+
+    /**
+     * Given a map and a set of keys, return a set containing the values referred-to by the keys.
+     * If the map is null or the keys are null, the EMPTY_SET is returned.
+     * If a passed key does not exist in the map, nothing is added to the set.
+     * However, if the key is present and maps to null, null is added to the set.
+     */
+    public static final Set fromMap(Map map, Object... keys) {
+        if (keys != null && map != null) {
+            Set answer = new HashSet();
+            for (Object key : keys) {
+                if (map.containsKey(key)) {
+                    answer.add(map.get(key));
+                }
+            }
+            return Collections.unmodifiableSet(answer);
+        }
+        return Collections.EMPTY_SET;
+    }
+
+    /**
+     * Given a comma-separated list of values, return a set of those values.
+     * If the passed string is null, the EMPTY_SET is returned.
+     * If the passed string is empty, the EMPTY_SET is returned.
+     */
+    public static final Set<String> fromCommaSeparatedValues(String csv) {
+        if (csv == null || csv.isEmpty()) {
+            return Collections.EMPTY_SET;
+        }
+        String[] tokens = csv.split(",");
+        return new HashSet<String>(Arrays.asList(tokens));
+    }
+}

cougar-framework/cougar-util/src/test/java/com/betfair/cougar/util/configuration/SetsTest.java

@@ -0,0 +1,102 @@
+package com.betfair.cougar.util.configuration;
+
+import org.junit.Test;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+import static org.junit.Assert.*;
+
+public class SetsTest {
+
+    /**
+     * Given a map and a set of keys, return a set containing the values referred-to by the keys.
+     */
+    @Test
+    public void testFromMap() {
+        Map m = new HashMap() {{
+            put("A", 1);
+            put("B", 2);
+            put("C", 3);
+        }};
+        Set s = Sets.fromMap(m, "A", "C");
+        assertTrue(s.contains(1));
+        assertFalse(s.contains(2));
+        assertTrue(s.contains(3));
+        assertEquals(2, s.size());
+    }
+
+    /**
+     * If the map is null or the keys are null, the EMPTY_SET is returned.
+     */
+    @Test
+    public void testFromMap_NullMap() {
+        assertEquals(Collections.EMPTY_SET, Sets.fromMap(null, "A"));
+    }
+
+    /**
+     * If the map is null or the keys are null, the EMPTY_SET is returned.
+     */
+    @Test
+    public void testFromMap_NullKeys() {
+        assertEquals(Collections.EMPTY_SET, Sets.fromMap(new HashMap(), null));
+    }
+
+    /**
+     * If a passed key does not exist in the map, nothing is added to the set.
+     */
+    @Test
+    public void testFromMap_MissingKey() {
+        Map m = new HashMap() {{
+            put("A", 1);
+        }};
+        Set s = Sets.fromMap(m, "A", "D");
+        assertTrue(s.contains(1));
+        assertEquals(1, s.size());
+    }
+
+    /**
+     * However, if the key is present and maps to null, null is added to the set.
+     */
+    @Test
+    public void testFromMap_KeyMappedToNull() {
+        Map m = new HashMap() {{
+            put("A", 1);
+            put("B", null);
+        }};
+        Set s = Sets.fromMap(m, "A", "B");
+        assertTrue(s.contains(1));
+        assertTrue(s.contains(null));
+        assertEquals(2, s.size());
+    }
+
+    /**
+     * Given a comma-separated list of values, return a set of those values.
+     */
+    @Test
+    public void testFromCommaSeparatedValues() {
+        Set s = Sets.fromCommaSeparatedValues("1,2,3");
+        assertTrue(s.contains("1"));
+        assertTrue(s.contains("2"));
+        assertTrue(s.contains("3"));
+        assertEquals(3, s.size());
+    }
+
+    /**
+     * If the passed string is null, the EMPTY_SET is returned.
+     */
+    @Test
+    public void testFromCommaSeparatedValues_NullInput() {
+        assertEquals(Collections.EMPTY_SET, Sets.fromCommaSeparatedValues(null));
+    }
+
+    /**
+     * If the passed string is empty, the EMPTY_SET is returned.
+     */
+    @Test
+    public void testFromCommaSeparatedValues_EmptyInput() {
+        assertEquals(Collections.EMPTY_SET, Sets.fromCommaSeparatedValues(""));
+    }
+}