Use empty array. (apache#61)

Author: arturobernalg

src/main/java/org/apache/commons/cli/GnuParser.java

@@ -85,6 +85,6 @@ protected String[] flatten(final Options options, final String[] arguments, fina
             }
         }
 
-        return tokens.toArray(new String[tokens.size()]);
+        return tokens.toArray(Util.EMPTY_STRING_ARRAY);
     }
 }

src/main/java/org/apache/commons/cli/PosixParser.java

@@ -176,7 +176,7 @@ else if (token.startsWith("-")) {
             gobble(iter);
         }
 
-        return tokens.toArray(new String[tokens.size()]);
+        return tokens.toArray(Util.EMPTY_STRING_ARRAY);
     }
 
     /**

src/main/java/org/apache/commons/cli/Util.java

@@ -21,6 +21,12 @@ Licensed to the Apache Software Foundation (ASF) under one or more
  * Contains useful helper methods for classes within this package.
  */
 final class Util {
+
+    /**
+     * An empty immutable {@code String} array.
+     */
+    static final String[] EMPTY_STRING_ARRAY = new String[0];
+
     /**
      * Remove the leading and trailing quotes from {@code str}. E.g. if str is '"one two"', then 'one two' is returned.
      *