CollectionUtils: Add iterableOf()

Author: kerrykimbrough

tcases-lib/src/main/java/org/cornutum/tcases/util/CollectionUtils.java

@@ -7,9 +7,13 @@
 
 package org.cornutum.tcases.util;
 
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
@@ -35,6 +39,14 @@ public static <T> Stream<T> toStream( Iterator<T> iterator)
     return StreamSupport.stream( iterable.spliterator(), false);
     }
 
+  /**
+   * If the given value is present, returns it as a singleton list. Otherwise, returns an empty list.
+   */
+  public static <T> List<T> iterableOf( Optional<T> value)
+    {
+    return value.map( Arrays::asList).orElse( Collections.emptyList());
+    }
+
   /**
    * Returns a stream containing the members of the given collection.
    */