Add TimestampedObserver.isClosed().

Author: garydgregory

src/changes/changes.xml

@@ -433,6 +433,9 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="add" due-to="Gary Gregory">
         Add IOConsumer.asConsumer().
       </action>
+      <action dev="ggregory" type="add" due-to="Gary Gregory">
+        Add TimestampedObserver.isClosed().
+      </action>
       <!-- UPDATE -->
       <action dev="kinow" type="update" due-to="Dependabot, Gary Gregory">
         Bump actions/cache from 2.1.6 to 3.0.7 #307, #337.

src/main/java/org/apache/commons/io/input/TimestampedObserver.java

@@ -86,6 +86,16 @@ public Duration getOpenToNowDuration() {
         return Duration.between(openInstant, Instant.now());
     }
 
+    /**
+     * Tests whether {@link #closed()} has been called.
+     *
+     * @return whether {@link #closed()} has been called.
+     * @since 2.12.0
+     */
+    public boolean isClosed() {
+        return closeInstant != null;
+    }
+
     @Override
     public String toString() {
         return "TimestampedObserver [openInstant=" + openInstant + ", closeInstant=" + closeInstant + "]";

src/test/java/org/apache/commons/io/input/TimestampedObserverTest.java

@@ -20,6 +20,7 @@
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
@@ -39,18 +40,22 @@ public void test() throws IOException, InterruptedException {
         // Some OS' clock granularity may be high.
         Thread.sleep(20);
         final TimestampedObserver timestampedObserver = new TimestampedObserver();
+        assertFalse(timestampedObserver.isClosed());
         // Java 8 instant resolution is not great.
         Thread.sleep(20);
         // toString() should not blow up before close().
         assertNotNull(timestampedObserver.toString());
         assertTrue(timestampedObserver.getOpenInstant().isAfter(before));
         assertTrue(timestampedObserver.getOpenToNowDuration().toNanos() > 0);
         assertNull(timestampedObserver.getCloseInstant());
+        assertFalse(timestampedObserver.isClosed());
         final byte[] buffer = MessageDigestCalculatingInputStreamTest.generateRandomByteStream(IOUtils.DEFAULT_BUFFER_SIZE);
         try (ObservableInputStream ois = new ObservableInputStream(new ByteArrayInputStream(buffer), timestampedObserver)) {
             assertTrue(timestampedObserver.getOpenInstant().isAfter(before));
             assertTrue(timestampedObserver.getOpenToNowDuration().toNanos() > 0);
+            assertFalse(timestampedObserver.isClosed());
         }
+        assertTrue(timestampedObserver.isClosed());
         assertTrue(timestampedObserver.getOpenInstant().isAfter(before));
         assertTrue(timestampedObserver.getOpenToNowDuration().toNanos() > 0);
         assertTrue(timestampedObserver.getCloseInstant().isAfter(timestampedObserver.getOpenInstant()));