Create Stream#pushBack() method

src/main/java/com/github/zafarkhaja/semver/util/Stream.java

@@ -115,6 +115,15 @@ public class Stream<E> implements Iterable<E> {
         throw new UnexpectedElementException(lookahead, expected);
     }
 
+    /**
+     * Pushes back one element at a time.
+     */
+    public void pushBack() {
+        if (offset > 0) {
+            offset--;
+        }
+    }
+
     /**
      * Returns the next element in this stream without consuming it.
      *

src/test/java/com/github/zafarkhaja/semver/util/StreamTest.java

@@ -203,4 +203,29 @@ public class StreamTest {
             }
         ));
     }
+
+    @Test
+    public void shouldPushBackOneElementAtATime() {
+        Stream<Character> stream = new Stream<Character>(
+            new Character[] {'a', 'b', 'c'}
+        );
+        assertEquals(Character.valueOf('a'), stream.consume());
+        stream.pushBack();
+        assertEquals(Character.valueOf('a'), stream.consume());
+    }
+
+    @Test
+    public void shouldStopPushingBackWhenThereAreNoElements() {
+        Stream<Character> stream = new Stream<Character>(
+            new Character[] {'a', 'b', 'c'}
+        );
+        assertEquals(Character.valueOf('a'), stream.consume());
+        assertEquals(Character.valueOf('b'), stream.consume());
+        assertEquals(Character.valueOf('c'), stream.consume());
+        stream.pushBack();
+        stream.pushBack();
+        stream.pushBack();
+        stream.pushBack();
+        assertEquals(Character.valueOf('a'), stream.consume());
+    }
 }