Fixed duplicate event issues, and added additional test

Author: Tanooj Luthra

src/main/java/com/box/sdk/LRUCache.java

@@ -14,9 +14,7 @@ public LRUCache() {
 
     boolean add(E item) {
         boolean newItem = !this.linkedHashSet.remove(item);
-        if (newItem) {
-            this.linkedHashSet.add(item);
-        }
+        this.linkedHashSet.add(item);
 
         if (this.linkedHashSet.size() >= MAX_SIZE) {
             Iterator<E> it = this.linkedHashSet.iterator();

src/test/java/com/box/sdk/LRUCacheTest.java

@@ -26,6 +26,16 @@ public void addReturnsFalseForExistingItem() {
         assertThat(added, is(false));
     }
 
+    @Category(UnitTest.class)
+    public void addReturnsFalseForExistingItemMultipleTimes() {
+        LRUCache<Integer> lru = new LRUCache<Integer>();
+        lru.add(1);
+        lru.add(1);
+        boolean added = lru.add(1);
+
+        assertThat(added, is(false));
+    }
+
     @Test
     @Category(UnitTest.class)
     public void addRemovesOldestItemWhenMaxSizeIsReached() {