src/share/classes/java/util/stream/Streams.java

rev 7962 : 8017513: Support for closeable streams
8022237: j.u.s.BaseStream.onClose() has an issue in implementation or requires spec clarification
8022572: Same exception instances thrown from j.u.stream.Stream.onClose() handlers are not listed as suppressed
Summary: BaseStream implements AutoCloseable; Remove CloseableStream and DelegatingStream
Reviewed-by:
Contributed-by: brian.goetz@oracle.com

@@ -831,6 +831,65 @@
             OfDouble(Spliterator.OfDouble aSpliterator, Spliterator.OfDouble bSpliterator) {
                 super(aSpliterator, bSpliterator);
             }
         }
     }
+
+    /**
+     * Given two Runnables, return a Runnable that executes both in sequence,
+     * even if the first throws an exception, and if both throw exceptions, add
+     * any exceptions thrown by the second as suppressed exceptions of the first.
+     */
+    static Runnable composeWithExceptions(Runnable a, Runnable b) {
+        return new Runnable() {
+            @Override
+            @SuppressWarnings("finally")
+            public void run() {
+                try {
+                    a.run();
+                }
+                catch (Throwable e1) {
+                    try {
+                        b.run();
+                    }
+                    catch (Throwable e2) {
+                        e1.addSuppressed(e2);
+                    }
+                    finally { // addSuppressed can throw exception
+                        throw e1;
+                    }
+                }
+                b.run();
+            }
+        };
+    }
+
+    /**
+     * Given two streams, return a Runnable that
+     * executes both of their {@link BaseStream#close} methods in sequence,
+     * even if the first throws an exception, and if both throw exceptions, add
+     * any exceptions thrown by the second as suppressed exceptions of the first.
+     */
+    static Runnable composedClose(BaseStream<?, ?> a, BaseStream<?, ?> b) {
+        return new Runnable() {
+            @Override
+            @SuppressWarnings("finally")
+            public void run() {
+                try {
+                    a.close();
+                }
+                catch (Throwable e1) {
+                    try {
+                        b.close();
+                    }
+                    catch (Throwable e2) {
+                        e1.addSuppressed(e2);
+                    }
+                    finally { // addSuppressed can throw exception
+                        throw e1;
+                    }
+                }
+                b.close();
+            }
+        };
+    }
 }